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	$68.61	3.830%	$71.2378	$71.24	$71.25	$71.20
Purchase #2	$150.94	5.387%	$159.0711	$159.07	$159.05	$159.10
Purchase #3	$166.32	11.467%	$185.3919	$185.39	$185.40	$185.40
Purchase #4	$243.74	5.204%	$256.4242	$256.42	$256.40	$256.40
Purchase #5	$81.98	12.518%	$92.2423	$92.24	$92.25	$92.20
Purchase #6	$204.66	3.711%	$212.2549	$212.25	$212.25	$212.30
Purchase #7	$79.64	12.359%	$89.4827	$89.48	$89.50	$89.50
7 purchase totals =	$995.89		$1,066.1049	$1,066.09	$1,066.10	$1,066.10