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	$189.51	3.228%	$195.6274	$195.63	$195.65	$195.60
Purchase #2	$175.84	11.382%	$195.8541	$195.85	$195.85	$195.90
Purchase #3	$66.98	7.180%	$71.7892	$71.79	$71.80	$71.80
Purchase #4	$209.95	12.424%	$236.0342	$236.03	$236.05	$236.00
Purchase #5	$21.25	9.689%	$23.3089	$23.31	$23.30	$23.30
Purchase #6	$76.57	9.303%	$83.6933	$83.69	$83.70	$83.70
Purchase #7	$185.40	6.192%	$196.88	$196.88	$196.90	$196.90
7 purchase totals =	$925.50		$1,003.1871	$1,003.18	$1,003.25	$1,003.20