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	$202.44	7.642%	$217.9105	$217.91	$217.90	$217.90
Purchase #2	$105.29	5.293%	$110.863	$110.86	$110.85	$110.90
Purchase #3	$165.89	11.840%	$185.5314	$185.53	$185.55	$185.50
Purchase #4	$115.59	9.743%	$126.8519	$126.85	$126.85	$126.90
Purchase #5	$152.35	12.727%	$171.7396	$171.74	$171.75	$171.70
Purchase #6	$55.28	11.150%	$61.4437	$61.44	$61.45	$61.40
Purchase #7	$92.59	7.769%	$99.7833	$99.78	$99.80	$99.80
7 purchase totals =	$889.43		$974.1234	$974.11	$974.15	$974.10