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	$197.83	13.219%	$223.9811	$223.98	$224.00	$224.00
Purchase #2	$53.27	9.717%	$58.4462	$58.45	$58.45	$58.40
Purchase #3	$193.94	11.639%	$216.5127	$216.51	$216.50	$216.50
Purchase #4	$210.25	10.165%	$231.6219	$231.62	$231.60	$231.60
Purchase #5	$54.51	9.815%	$59.8602	$59.86	$59.85	$59.90
Purchase #6	$176.74	13.219%	$200.1033	$200.10	$200.10	$200.10
Purchase #7	$171.75	11.754%	$191.9375	$191.94	$191.95	$191.90
7 purchase totals =	$1,058.29		$1,182.4629	$1,182.46	$1,182.45	$1,182.40