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	$68.89	4.708%	$72.1333	$72.13	$72.15	$72.10
Purchase #2	$225.29	12.352%	$253.1178	$253.12	$253.10	$253.10
Purchase #3	$221.72	9.646%	$243.1071	$243.11	$243.10	$243.10
Purchase #4	$157.48	10.583%	$174.1461	$174.15	$174.15	$174.10
Purchase #5	$181.91	5.641%	$192.1715	$192.17	$192.15	$192.20
Purchase #6	$218.37	13.811%	$248.5291	$248.53	$248.55	$248.50
Purchase #7	$127.70	13.142%	$144.4823	$144.48	$144.50	$144.50
7 purchase totals =	$1,201.36		$1,327.6872	$1,327.69	$1,327.70	$1,327.60