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	$244.66	3.545%	$253.3332	$253.33	$253.35	$253.30
Purchase #2	$174.26	6.273%	$185.1913	$185.19	$185.20	$185.20
Purchase #3	$56.36	5.226%	$59.3054	$59.31	$59.30	$59.30
Purchase #4	$50.80	6.162%	$53.9303	$53.93	$53.95	$53.90
Purchase #5	$122.34	9.198%	$133.5928	$133.59	$133.60	$133.60
Purchase #6	$178.97	5.212%	$188.2979	$188.30	$188.30	$188.30
Purchase #7	$195.67	7.267%	$209.8893	$209.89	$209.90	$209.90
7 purchase totals =	$1,023.06		$1,083.5402	$1,083.54	$1,083.60	$1,083.50