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	$20.27	8.275%	$21.9473	$21.95	$21.95	$21.90
Purchase #2	$136.33	3.769%	$141.4683	$141.47	$141.45	$141.50
Purchase #3	$133.64	6.344%	$142.1181	$142.12	$142.10	$142.10
Purchase #4	$46.92	7.611%	$50.4911	$50.49	$50.50	$50.50
Purchase #5	$148.72	7.274%	$159.5379	$159.54	$159.55	$159.50
Purchase #6	$90.92	12.505%	$102.2895	$102.29	$102.30	$102.30
Purchase #7	$97.54	8.849%	$106.1713	$106.17	$106.15	$106.20
7 purchase totals =	$674.34		$724.0235	$724.03	$724.00	$724.00