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	$55.76	11.460%	$62.1501	$62.15	$62.15	$62.20
Purchase #2	$131.82	13.769%	$149.9703	$149.97	$149.95	$150.00
Purchase #3	$185.52	8.200%	$200.7326	$200.73	$200.75	$200.70
Purchase #4	$242.54	4.663%	$253.8496	$253.85	$253.85	$253.80
Purchase #5	$114.75	8.339%	$124.319	$124.32	$124.30	$124.30
Purchase #6	$153.37	12.564%	$172.6394	$172.64	$172.65	$172.60
Purchase #7	$150.84	11.200%	$167.7341	$167.73	$167.75	$167.70
7 purchase totals =	$1,034.60		$1,131.3951	$1,131.39	$1,131.40	$1,131.30