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	$92.48	3.581%	$95.7917	$95.79	$95.80	$95.80
Purchase #2	$196.61	11.411%	$219.0452	$219.05	$219.05	$219.00
Purchase #3	$180.39	10.464%	$199.266	$199.27	$199.25	$199.30
Purchase #4	$165.39	4.334%	$172.558	$172.56	$172.55	$172.60
Purchase #5	$173.69	9.761%	$190.6439	$190.64	$190.65	$190.60
Purchase #6	$88.87	11.796%	$99.3531	$99.35	$99.35	$99.40
Purchase #7	$106.53	10.284%	$117.4855	$117.49	$117.50	$117.50
7 purchase totals =	$1,003.96		$1,094.1434	$1,094.15	$1,094.15	$1,094.20