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	$130.70	10.602%	$144.5568	$144.56	$144.55	$144.60
Purchase #2	$6.51	12.636%	$7.3326	$7.33	$7.35	$7.30
Purchase #3	$229.62	10.417%	$253.5395	$253.54	$253.55	$253.50
Purchase #4	$71.67	3.403%	$74.1089	$74.11	$74.10	$74.10
Purchase #5	$71.72	11.727%	$80.1306	$80.13	$80.15	$80.10
Purchase #6	$216.64	10.312%	$238.9799	$238.98	$239.00	$239.00
Purchase #7	$40.79	12.206%	$45.7688	$45.77	$45.75	$45.80
7 purchase totals =	$767.65		$844.4171	$844.42	$844.45	$844.40