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	$77.27	12.417%	$86.8646	$86.86	$86.85	$86.90
Purchase #2	$157.75	8.367%	$170.9489	$170.95	$170.95	$170.90
Purchase #3	$83.49	8.131%	$90.2786	$90.28	$90.30	$90.30
Purchase #4	$248.74	9.274%	$271.8081	$271.81	$271.80	$271.80
Purchase #5	$161.69	7.869%	$174.4134	$174.41	$174.40	$174.40
Purchase #6	$143.29	5.464%	$151.1194	$151.12	$151.10	$151.10
Purchase #7	$138.66	7.164%	$148.5936	$148.59	$148.60	$148.60
7 purchase totals =	$1,010.89		$1,094.0266	$1,094.02	$1,094.00	$1,094.00