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	$243.81	7.525%	$262.1567	$262.16	$262.15	$262.20
Purchase #2	$189.94	10.637%	$210.1439	$210.14	$210.15	$210.10
Purchase #3	$52.61	13.777%	$59.8581	$59.86	$59.85	$59.90
Purchase #4	$212.44	12.761%	$239.5495	$239.55	$239.55	$239.50
Purchase #5	$129.44	13.113%	$146.4135	$146.41	$146.40	$146.40
Purchase #6	$41.34	10.210%	$45.5608	$45.56	$45.55	$45.60
Purchase #7	$42.44	6.166%	$45.0569	$45.06	$45.05	$45.10
7 purchase totals =	$912.02		$1,008.7394	$1,008.74	$1,008.70	$1,008.80