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	$223.58	10.235%	$246.4634	$246.46	$246.45	$246.50
Purchase #2	$175.66	4.814%	$184.1163	$184.12	$184.10	$184.10
Purchase #3	$172.99	7.227%	$185.492	$185.49	$185.50	$185.50
Purchase #4	$99.61	8.538%	$108.1147	$108.11	$108.10	$108.10
Purchase #5	$129.27	9.324%	$141.3231	$141.32	$141.30	$141.30
Purchase #6	$75.90	10.241%	$83.6729	$83.67	$83.65	$83.70
Purchase #7	$76.84	7.271%	$82.427	$82.43	$82.45	$82.40
7 purchase totals =	$953.85		$1,031.6094	$1,031.60	$1,031.55	$1,031.60