Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$216.58	6.601%	$230.8764	$230.88	$230.90	$230.90
Purchase #2	$101.27	4.475%	$105.8018	$105.80	$105.80	$105.80
Purchase #3	$240.59	4.448%	$251.2914	$251.29	$251.30	$251.30
Purchase #4	$54.54	3.588%	$56.4969	$56.50	$56.50	$56.50
Purchase #5	$140.81	10.282%	$155.2881	$155.29	$155.30	$155.30
Purchase #6	$230.98	13.197%	$261.4624	$261.46	$261.45	$261.50
Purchase #7	$193.55	12.722%	$218.1734	$218.17	$218.15	$218.20
7 purchase totals =	$1,178.32		$1,279.3904	$1,279.39	$1,279.40	$1,279.50