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	$151.94	10.726%	$168.2371	$168.24	$168.25	$168.20
Purchase #2	$159.66	3.420%	$165.1204	$165.12	$165.10	$165.10
Purchase #3	$143.68	5.871%	$152.1155	$152.12	$152.10	$152.10
Purchase #4	$224.50	11.516%	$250.3534	$250.35	$250.35	$250.40
Purchase #5	$23.46	3.640%	$24.3139	$24.31	$24.30	$24.30
Purchase #6	$193.96	11.315%	$215.9066	$215.91	$215.90	$215.90
Purchase #7	$168.39	4.827%	$176.5182	$176.52	$176.50	$176.50
7 purchase totals =	$1,065.59		$1,152.5651	$1,152.57	$1,152.50	$1,152.50