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	$54.38	13.490%	$61.7159	$61.72	$61.70	$61.70
Purchase #2	$220.36	5.225%	$231.8738	$231.87	$231.85	$231.90
Purchase #3	$94.34	10.727%	$104.4599	$104.46	$104.45	$104.50
Purchase #4	$250.97	13.582%	$285.0567	$285.06	$285.05	$285.10
Purchase #5	$223.30	3.521%	$231.1624	$231.16	$231.15	$231.20
Purchase #6	$172.33	9.580%	$188.8392	$188.84	$188.85	$188.80
Purchase #7	$40.74	6.483%	$43.3812	$43.38	$43.40	$43.40
7 purchase totals =	$1,056.42		$1,146.4891	$1,146.49	$1,146.45	$1,146.60