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	$186.55	4.735%	$195.3831	$195.38	$195.40	$195.40
Purchase #2	$203.46	10.741%	$225.3136	$225.31	$225.30	$225.30
Purchase #3	$141.80	10.557%	$156.7698	$156.77	$156.75	$156.80
Purchase #4	$218.88	4.677%	$229.117	$229.12	$229.10	$229.10
Purchase #5	$43.29	6.480%	$46.0952	$46.10	$46.10	$46.10
Purchase #6	$57.74	10.261%	$63.6647	$63.66	$63.65	$63.70
Purchase #7	$111.52	10.446%	$123.1694	$123.17	$123.15	$123.20
7 purchase totals =	$963.24		$1,039.5128	$1,039.51	$1,039.45	$1,039.60