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	$141.49	9.629%	$155.1141	$155.11	$155.10	$155.10
Purchase #2	$81.87	8.619%	$88.9264	$88.93	$88.95	$88.90
Purchase #3	$116.87	9.406%	$127.8628	$127.86	$127.85	$127.90
Purchase #4	$135.42	10.266%	$149.3222	$149.32	$149.30	$149.30
Purchase #5	$147.72	6.593%	$157.4592	$157.46	$157.45	$157.50
Purchase #6	$91.82	4.715%	$96.1493	$96.15	$96.15	$96.10
Purchase #7	$151.59	9.710%	$166.3094	$166.31	$166.30	$166.30
7 purchase totals =	$866.78		$941.1434	$941.14	$941.10	$941.10