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	$147.45	6.423%	$156.9207	$156.92	$156.90	$156.90
Purchase #2	$202.97	3.803%	$210.6889	$210.69	$210.70	$210.70
Purchase #3	$89.88	12.227%	$100.8696	$100.87	$100.85	$100.90
Purchase #4	$31.58	12.461%	$35.5152	$35.52	$35.50	$35.50
Purchase #5	$233.70	9.413%	$255.6982	$255.70	$255.70	$255.70
Purchase #6	$133.66	10.392%	$147.5499	$147.55	$147.55	$147.50
Purchase #7	$129.91	7.657%	$139.8572	$139.86	$139.85	$139.90
7 purchase totals =	$969.15		$1,047.0997	$1,047.11	$1,047.05	$1,047.10