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	$204.85	9.292%	$223.8847	$223.88	$223.90	$223.90
Purchase #2	$247.63	11.200%	$275.3646	$275.36	$275.35	$275.40
Purchase #3	$165.88	6.285%	$176.3056	$176.31	$176.30	$176.30
Purchase #4	$239.77	4.337%	$250.1688	$250.17	$250.15	$250.20
Purchase #5	$140.78	8.551%	$152.8181	$152.82	$152.80	$152.80
Purchase #6	$235.74	6.287%	$250.561	$250.56	$250.55	$250.60
Purchase #7	$67.85	6.172%	$72.0377	$72.04	$72.05	$72.00
7 purchase totals =	$1,302.50		$1,401.1405	$1,401.14	$1,401.10	$1,401.20