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	$158.94	6.489%	$169.2536	$169.25	$169.25	$169.30
Purchase #2	$204.66	8.415%	$221.8821	$221.88	$221.90	$221.90
Purchase #3	$182.61	11.491%	$203.5937	$203.59	$203.60	$203.60
Purchase #4	$78.89	12.818%	$89.0021	$89.00	$89.00	$89.00
Purchase #5	$230.33	10.372%	$254.2198	$254.22	$254.20	$254.20
Purchase #6	$56.67	10.625%	$62.6912	$62.69	$62.70	$62.70
Purchase #7	$230.91	5.805%	$244.3143	$244.31	$244.30	$244.30
7 purchase totals =	$1,143.01		$1,244.9568	$1,244.94	$1,244.95	$1,245.00