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	$133.88	11.738%	$149.5948	$149.59	$149.60	$149.60
Purchase #2	$200.39	11.676%	$223.7875	$223.79	$223.80	$223.80
Purchase #3	$210.34	9.327%	$229.9584	$229.96	$229.95	$230.00
Purchase #4	$188.34	6.400%	$200.3938	$200.39	$200.40	$200.40
Purchase #5	$127.36	5.563%	$134.445	$134.45	$134.45	$134.40
Purchase #6	$57.31	5.668%	$60.5583	$60.56	$60.55	$60.60
Purchase #7	$82.84	8.612%	$89.9742	$89.97	$89.95	$90.00
7 purchase totals =	$1,000.46		$1,088.7120	$1,088.71	$1,088.70	$1,088.80