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	$184.56	13.510%	$209.4941	$209.49	$209.50	$209.50
Purchase #2	$11.63	7.822%	$12.5397	$12.54	$12.55	$12.50
Purchase #3	$85.26	13.617%	$96.8699	$96.87	$96.85	$96.90
Purchase #4	$245.41	10.687%	$271.637	$271.64	$271.65	$271.60
Purchase #5	$73.78	12.704%	$83.153	$83.15	$83.15	$83.20
Purchase #6	$210.29	4.529%	$219.814	$219.81	$219.80	$219.80
Purchase #7	$147.85	3.191%	$152.5679	$152.57	$152.55	$152.60
7 purchase totals =	$958.78		$1,046.0756	$1,046.07	$1,046.05	$1,046.10