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	$59.76	5.115%	$62.8167	$62.82	$62.80	$62.80
Purchase #2	$81.37	9.700%	$89.2629	$89.26	$89.25	$89.30
Purchase #3	$63.49	12.112%	$71.1799	$71.18	$71.20	$71.20
Purchase #4	$241.86	5.740%	$255.7428	$255.74	$255.75	$255.70
Purchase #5	$129.30	5.579%	$136.5136	$136.51	$136.50	$136.50
Purchase #6	$30.38	12.247%	$34.1006	$34.10	$34.10	$34.10
Purchase #7	$209.45	3.420%	$216.6132	$216.61	$216.60	$216.60
7 purchase totals =	$815.61		$866.2297	$866.22	$866.20	$866.20