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	$125.53	11.454%	$139.9082	$139.91	$139.90	$139.90
Purchase #2	$85.95	10.847%	$95.273	$95.27	$95.25	$95.30
Purchase #3	$159.55	13.473%	$181.0462	$181.05	$181.05	$181.00
Purchase #4	$206.59	8.380%	$223.9022	$223.90	$223.90	$223.90
Purchase #5	$241.34	13.667%	$274.3239	$274.32	$274.30	$274.30
Purchase #6	$95.67	4.638%	$100.1072	$100.11	$100.10	$100.10
Purchase #7	$201.73	4.480%	$210.7675	$210.77	$210.75	$210.80
7 purchase totals =	$1,116.36		$1,225.3282	$1,225.33	$1,225.25	$1,225.30