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	$85.57	4.758%	$89.6414	$89.64	$89.65	$89.60
Purchase #2	$89.74	6.342%	$95.4313	$95.43	$95.45	$95.40
Purchase #3	$56.73	10.796%	$62.8546	$62.85	$62.85	$62.90
Purchase #4	$6.84	5.709%	$7.2305	$7.23	$7.25	$7.20
Purchase #5	$41.65	8.670%	$45.2611	$45.26	$45.25	$45.30
Purchase #6	$156.29	11.835%	$174.7869	$174.79	$174.80	$174.80
Purchase #7	$10.31	9.317%	$11.2706	$11.27	$11.25	$11.30
7 purchase totals =	$447.13		$486.4764	$486.47	$486.50	$486.50