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	$185.39	11.132%	$206.0276	$206.03	$206.05	$206.00
Purchase #2	$32.86	5.761%	$34.7531	$34.75	$34.75	$34.80
Purchase #3	$68.72	5.543%	$72.5291	$72.53	$72.55	$72.50
Purchase #4	$38.61	8.413%	$41.8583	$41.86	$41.85	$41.90
Purchase #5	$54.82	6.792%	$58.5434	$58.54	$58.55	$58.50
Purchase #6	$100.41	7.414%	$107.8544	$107.85	$107.85	$107.90
Purchase #7	$185.95	13.118%	$210.3429	$210.34	$210.35	$210.30
7 purchase totals =	$666.76		$731.9088	$731.90	$731.95	$731.90