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	$244.68	12.737%	$275.8449	$275.84	$275.85	$275.80
Purchase #2	$31.47	12.449%	$35.3877	$35.39	$35.40	$35.40
Purchase #3	$139.32	5.107%	$146.4351	$146.44	$146.45	$146.40
Purchase #4	$92.52	7.390%	$99.3572	$99.36	$99.35	$99.40
Purchase #5	$118.35	8.697%	$128.6429	$128.64	$128.65	$128.60
Purchase #6	$204.76	8.408%	$221.9762	$221.98	$222.00	$222.00
Purchase #7	$179.57	12.415%	$201.8636	$201.86	$201.85	$201.90
7 purchase totals =	$1,010.67		$1,109.5076	$1,109.51	$1,109.55	$1,109.50