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	$232.35	5.153%	$244.323	$244.32	$244.30	$244.30
Purchase #2	$30.81	6.494%	$32.8108	$32.81	$32.80	$32.80
Purchase #3	$80.32	6.492%	$85.5344	$85.53	$85.55	$85.50
Purchase #4	$223.47	8.568%	$242.6169	$242.62	$242.60	$242.60
Purchase #5	$66.33	10.658%	$73.3995	$73.40	$73.40	$73.40
Purchase #6	$245.60	4.276%	$256.1019	$256.10	$256.10	$256.10
Purchase #7	$25.52	11.254%	$28.392	$28.39	$28.40	$28.40
7 purchase totals =	$904.40		$963.1785	$963.17	$963.15	$963.10