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	$127.49	11.627%	$142.3133	$142.31	$142.30	$142.30
Purchase #2	$71.42	11.781%	$79.834	$79.83	$79.85	$79.80
Purchase #3	$118.84	5.483%	$125.356	$125.36	$125.35	$125.40
Purchase #4	$229.28	5.684%	$242.3123	$242.31	$242.30	$242.30
Purchase #5	$14.88	13.450%	$16.8814	$16.88	$16.90	$16.90
Purchase #6	$151.90	13.419%	$172.2835	$172.28	$172.30	$172.30
Purchase #7	$111.35	11.691%	$124.3679	$124.37	$124.35	$124.40
7 purchase totals =	$825.16		$903.3484	$903.34	$903.35	$903.40