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	$168.69	4.816%	$176.8141	$176.81	$176.80	$176.80
Purchase #2	$104.58	7.610%	$112.5385	$112.54	$112.55	$112.50
Purchase #3	$139.69	4.687%	$146.2373	$146.24	$146.25	$146.20
Purchase #4	$225.76	8.443%	$244.8209	$244.82	$244.80	$244.80
Purchase #5	$242.55	3.142%	$250.1709	$250.17	$250.15	$250.20
Purchase #6	$53.55	11.657%	$59.7923	$59.79	$59.80	$59.80
Purchase #7	$46.40	3.791%	$48.159	$48.16	$48.15	$48.20
7 purchase totals =	$981.22		$1,038.5330	$1,038.53	$1,038.50	$1,038.50