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	$59.38	6.781%	$63.4066	$63.41	$63.40	$63.40
Purchase #2	$86.92	11.815%	$97.1896	$97.19	$97.20	$97.20
Purchase #3	$230.64	10.516%	$254.8941	$254.89	$254.90	$254.90
Purchase #4	$236.75	4.559%	$247.5434	$247.54	$247.55	$247.50
Purchase #5	$116.86	9.843%	$128.3625	$128.36	$128.35	$128.40
Purchase #6	$247.92	6.131%	$263.12	$263.12	$263.10	$263.10
Purchase #7	$121.53	5.165%	$127.807	$127.81	$127.80	$127.80
7 purchase totals =	$1,100.00		$1,182.3232	$1,182.32	$1,182.30	$1,182.30