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	$128.33	11.552%	$143.1547	$143.15	$143.15	$143.20
Purchase #2	$152.46	8.382%	$165.2392	$165.24	$165.25	$165.20
Purchase #3	$250.48	9.427%	$274.0927	$274.09	$274.10	$274.10
Purchase #4	$163.86	13.452%	$185.9024	$185.90	$185.90	$185.90
Purchase #5	$228.39	9.254%	$249.5252	$249.53	$249.55	$249.50
Purchase #6	$241.35	9.600%	$264.5196	$264.52	$264.50	$264.50
Purchase #7	$127.98	9.114%	$139.6441	$139.64	$139.65	$139.60
7 purchase totals =	$1,292.85		$1,422.0779	$1,422.07	$1,422.10	$1,422.00