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	$175.41	8.286%	$189.9445	$189.94	$189.95	$189.90
Purchase #2	$222.68	6.569%	$237.3078	$237.31	$237.30	$237.30
Purchase #3	$53.51	11.649%	$59.7434	$59.74	$59.75	$59.70
Purchase #4	$27.84	3.857%	$28.9138	$28.91	$28.90	$28.90
Purchase #5	$104.61	6.312%	$111.213	$111.21	$111.20	$111.20
Purchase #6	$228.59	11.808%	$255.5819	$255.58	$255.60	$255.60
Purchase #7	$179.34	12.144%	$201.119	$201.12	$201.10	$201.10
7 purchase totals =	$991.98		$1,083.8234	$1,083.81	$1,083.80	$1,083.70