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	$197.64	12.139%	$221.6315	$221.63	$221.65	$221.60
Purchase #2	$130.25	4.690%	$136.3587	$136.36	$136.35	$136.40
Purchase #3	$171.53	11.717%	$191.6282	$191.63	$191.65	$191.60
Purchase #4	$110.57	13.292%	$125.267	$125.27	$125.25	$125.30
Purchase #5	$235.93	6.315%	$250.829	$250.83	$250.85	$250.80
Purchase #6	$98.27	6.387%	$104.5465	$104.55	$104.55	$104.50
Purchase #7	$106.27	4.570%	$111.1265	$111.13	$111.15	$111.10
7 purchase totals =	$1,050.46		$1,141.3874	$1,141.40	$1,141.45	$1,141.30