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	$60.61	3.124%	$62.5035	$62.50	$62.50	$62.50
Purchase #2	$25.77	8.301%	$27.9092	$27.91	$27.90	$27.90
Purchase #3	$81.56	11.366%	$90.8301	$90.83	$90.85	$90.80
Purchase #4	$235.31	12.790%	$265.4061	$265.41	$265.40	$265.40
Purchase #5	$234.86	10.119%	$258.6255	$258.63	$258.65	$258.60
Purchase #6	$250.31	6.155%	$265.7166	$265.72	$265.70	$265.70
Purchase #7	$55.89	9.840%	$61.3896	$61.39	$61.40	$61.40
7 purchase totals =	$944.31		$1,032.3806	$1,032.39	$1,032.40	$1,032.30