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	$172.58	12.736%	$194.5598	$194.56	$194.55	$194.60
Purchase #2	$222.79	3.511%	$230.6122	$230.61	$230.60	$230.60
Purchase #3	$104.96	13.651%	$119.2881	$119.29	$119.30	$119.30
Purchase #4	$246.89	10.142%	$271.9296	$271.93	$271.95	$271.90
Purchase #5	$68.97	7.142%	$73.8958	$73.90	$73.90	$73.90
Purchase #6	$235.32	12.416%	$264.5373	$264.54	$264.55	$264.50
Purchase #7	$78.97	13.498%	$89.6294	$89.63	$89.65	$89.60
7 purchase totals =	$1,130.48		$1,244.4522	$1,244.46	$1,244.50	$1,244.40