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	$165.72	8.672%	$180.0912	$180.09	$180.10	$180.10
Purchase #2	$77.53	11.658%	$86.5684	$86.57	$86.55	$86.60
Purchase #3	$19.40	3.822%	$20.1415	$20.14	$20.15	$20.10
Purchase #4	$244.58	4.363%	$255.251	$255.25	$255.25	$255.30
Purchase #5	$189.72	8.873%	$206.5539	$206.55	$206.55	$206.60
Purchase #6	$191.49	10.547%	$211.6865	$211.69	$211.70	$211.70
Purchase #7	$165.34	12.784%	$186.4771	$186.48	$186.50	$186.50
7 purchase totals =	$1,053.78		$1,146.7696	$1,146.77	$1,146.80	$1,146.90