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	$86.71	3.510%	$89.7535	$89.75	$89.75	$89.80
Purchase #2	$156.37	5.290%	$164.642	$164.64	$164.65	$164.60
Purchase #3	$195.37	7.374%	$209.7766	$209.78	$209.80	$209.80
Purchase #4	$43.86	3.115%	$45.2262	$45.23	$45.25	$45.20
Purchase #5	$238.94	12.822%	$269.5769	$269.58	$269.60	$269.60
Purchase #6	$138.55	10.113%	$152.5616	$152.56	$152.55	$152.60
Purchase #7	$71.95	13.761%	$81.851	$81.85	$81.85	$81.90
7 purchase totals =	$931.75		$1,013.3878	$1,013.39	$1,013.45	$1,013.50