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	$153.32	9.504%	$167.8915	$167.89	$167.90	$167.90
Purchase #2	$169.89	8.679%	$184.6348	$184.63	$184.65	$184.60
Purchase #3	$98.63	4.825%	$103.3889	$103.39	$103.40	$103.40
Purchase #4	$111.26	3.675%	$115.3488	$115.35	$115.35	$115.30
Purchase #5	$132.88	11.506%	$148.1692	$148.17	$148.15	$148.20
Purchase #6	$142.40	6.443%	$151.5748	$151.57	$151.55	$151.60
Purchase #7	$35.95	3.564%	$37.2313	$37.23	$37.25	$37.20
7 purchase totals =	$844.33		$908.2393	$908.23	$908.25	$908.20