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	$166.71	11.745%	$186.2901	$186.29	$186.30	$186.30
Purchase #2	$73.34	11.285%	$81.6164	$81.62	$81.60	$81.60
Purchase #3	$103.94	7.401%	$111.6326	$111.63	$111.65	$111.60
Purchase #4	$104.36	12.795%	$117.7129	$117.71	$117.70	$117.70
Purchase #5	$33.72	6.456%	$35.897	$35.90	$35.90	$35.90
Purchase #6	$127.27	4.312%	$132.7579	$132.76	$132.75	$132.80
Purchase #7	$169.33	11.169%	$188.2425	$188.24	$188.25	$188.20
7 purchase totals =	$778.67		$854.1494	$854.15	$854.15	$854.10