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	$187.91	7.176%	$201.3944	$201.39	$201.40	$201.40
Purchase #2	$97.86	10.700%	$108.331	$108.33	$108.35	$108.30
Purchase #3	$104.66	7.140%	$112.1327	$112.13	$112.15	$112.10
Purchase #4	$150.79	10.616%	$166.7979	$166.80	$166.80	$166.80
Purchase #5	$125.46	13.419%	$142.2955	$142.30	$142.30	$142.30
Purchase #6	$124.71	5.164%	$131.15	$131.15	$131.15	$131.20
Purchase #7	$247.67	5.710%	$261.812	$261.81	$261.80	$261.80
7 purchase totals =	$1,039.06		$1,123.9135	$1,123.91	$1,123.95	$1,123.90