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	$103.47	10.385%	$114.2154	$114.22	$114.20	$114.20
Purchase #2	$52.90	10.605%	$58.51	$58.51	$58.50	$58.50
Purchase #3	$99.79	11.607%	$111.3726	$111.37	$111.35	$111.40
Purchase #4	$177.56	6.104%	$188.3983	$188.40	$188.40	$188.40
Purchase #5	$140.33	6.144%	$148.9519	$148.95	$148.95	$149.00
Purchase #6	$111.72	6.391%	$118.86	$118.86	$118.85	$118.90
Purchase #7	$238.58	3.123%	$246.0309	$246.03	$246.05	$246.00
7 purchase totals =	$924.35		$986.3391	$986.34	$986.30	$986.40