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	$165.47	10.552%	$182.9304	$182.93	$182.95	$182.90
Purchase #2	$170.42	13.286%	$193.062	$193.06	$193.05	$193.10
Purchase #3	$96.48	6.166%	$102.429	$102.43	$102.45	$102.40
Purchase #4	$247.51	9.824%	$271.8254	$271.83	$271.85	$271.80
Purchase #5	$83.56	5.779%	$88.3889	$88.39	$88.40	$88.40
Purchase #6	$46.64	11.530%	$52.0176	$52.02	$52.00	$52.00
Purchase #7	$229.53	5.121%	$241.2842	$241.28	$241.30	$241.30
7 purchase totals =	$1,039.61		$1,131.9375	$1,131.94	$1,132.00	$1,131.90