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	$36.29	13.374%	$41.1434	$41.14	$41.15	$41.10
Purchase #2	$239.64	9.302%	$261.9313	$261.93	$261.95	$261.90
Purchase #3	$72.51	8.293%	$78.5233	$78.52	$78.50	$78.50
Purchase #4	$67.37	6.727%	$71.902	$71.90	$71.90	$71.90
Purchase #5	$49.63	10.576%	$54.8789	$54.88	$54.90	$54.90
Purchase #6	$212.42	3.829%	$220.5536	$220.55	$220.55	$220.60
Purchase #7	$88.86	11.842%	$99.3828	$99.38	$99.40	$99.40
7 purchase totals =	$766.72		$828.3153	$828.30	$828.35	$828.30