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	$93.61	13.652%	$106.3896	$106.39	$106.40	$106.40
Purchase #2	$188.96	10.752%	$209.277	$209.28	$209.30	$209.30
Purchase #3	$222.78	6.786%	$237.8979	$237.90	$237.90	$237.90
Purchase #4	$141.82	13.417%	$160.848	$160.85	$160.85	$160.80
Purchase #5	$161.33	3.445%	$166.8878	$166.89	$166.90	$166.90
Purchase #6	$188.31	5.685%	$199.0154	$199.02	$199.00	$199.00
Purchase #7	$11.87	11.829%	$13.2741	$13.27	$13.25	$13.30
7 purchase totals =	$1,008.68		$1,093.5898	$1,093.60	$1,093.60	$1,093.60