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	$213.42	4.446%	$222.9087	$222.91	$222.90	$222.90
Purchase #2	$186.54	5.474%	$196.7512	$196.75	$196.75	$196.80
Purchase #3	$28.28	11.408%	$31.5062	$31.51	$31.50	$31.50
Purchase #4	$41.62	12.171%	$46.6856	$46.69	$46.70	$46.70
Purchase #5	$231.64	13.714%	$263.4071	$263.41	$263.40	$263.40
Purchase #6	$28.86	13.208%	$32.6718	$32.67	$32.65	$32.70
Purchase #7	$242.58	7.715%	$261.295	$261.30	$261.30	$261.30
7 purchase totals =	$972.94		$1,055.2256	$1,055.24	$1,055.20	$1,055.30