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	$158.72	5.274%	$167.0909	$167.09	$167.10	$167.10
Purchase #2	$84.70	5.654%	$89.4889	$89.49	$89.50	$89.50
Purchase #3	$71.73	8.615%	$77.9095	$77.91	$77.90	$77.90
Purchase #4	$129.79	9.209%	$141.7424	$141.74	$141.75	$141.70
Purchase #5	$74.55	5.731%	$78.8225	$78.82	$78.80	$78.80
Purchase #6	$211.30	9.348%	$231.0523	$231.05	$231.05	$231.10
Purchase #7	$84.44	10.584%	$93.3771	$93.38	$93.40	$93.40
7 purchase totals =	$815.23		$879.4836	$879.48	$879.50	$879.50