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	$240.31	10.571%	$265.7132	$265.71	$265.70	$265.70
Purchase #2	$211.35	11.835%	$236.3633	$236.36	$236.35	$236.40
Purchase #3	$66.82	6.639%	$71.2562	$71.26	$71.25	$71.30
Purchase #4	$234.39	13.166%	$265.2498	$265.25	$265.25	$265.20
Purchase #5	$222.33	8.748%	$241.7794	$241.78	$241.80	$241.80
Purchase #6	$233.74	12.432%	$262.7986	$262.80	$262.80	$262.80
Purchase #7	$93.33	7.220%	$100.0684	$100.07	$100.05	$100.10
7 purchase totals =	$1,302.27		$1,443.2289	$1,443.23	$1,443.20	$1,443.30