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	$145.61	13.668%	$165.512	$165.51	$165.50	$165.50
Purchase #2	$194.82	10.741%	$215.7456	$215.75	$215.75	$215.70
Purchase #3	$195.95	13.865%	$223.1185	$223.12	$223.10	$223.10
Purchase #4	$150.70	9.121%	$164.4453	$164.45	$164.45	$164.40
Purchase #5	$243.28	13.462%	$276.0304	$276.03	$276.05	$276.00
Purchase #6	$195.37	3.306%	$201.8289	$201.83	$201.85	$201.80
Purchase #7	$189.76	3.675%	$196.7337	$196.73	$196.75	$196.70
7 purchase totals =	$1,315.49		$1,443.4144	$1,443.42	$1,443.45	$1,443.20