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	$54.27	13.444%	$61.5661	$61.57	$61.55	$61.60
Purchase #2	$146.25	4.460%	$152.7728	$152.77	$152.75	$152.80
Purchase #3	$237.90	3.231%	$245.5865	$245.59	$245.60	$245.60
Purchase #4	$214.65	7.148%	$229.9932	$229.99	$230.00	$230.00
Purchase #5	$78.91	5.322%	$83.1096	$83.11	$83.10	$83.10
Purchase #6	$74.61	4.616%	$78.054	$78.05	$78.05	$78.10
Purchase #7	$104.57	10.582%	$115.6356	$115.64	$115.65	$115.60
7 purchase totals =	$911.16		$966.7178	$966.72	$966.70	$966.80