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	$106.75	7.628%	$114.8929	$114.89	$114.90	$114.90
Purchase #2	$122.96	10.752%	$136.1807	$136.18	$136.20	$136.20
Purchase #3	$163.30	10.513%	$180.4677	$180.47	$180.45	$180.50
Purchase #4	$205.82	6.362%	$218.9143	$218.91	$218.90	$218.90
Purchase #5	$240.29	6.353%	$255.5556	$255.56	$255.55	$255.60
Purchase #6	$91.33	8.337%	$98.9442	$98.94	$98.95	$98.90
Purchase #7	$26.27	3.641%	$27.2265	$27.23	$27.25	$27.20
7 purchase totals =	$956.72		$1,032.1819	$1,032.18	$1,032.20	$1,032.20