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	$41.80	13.215%	$47.3239	$47.32	$47.30	$47.30
Purchase #2	$52.83	11.851%	$59.0909	$59.09	$59.10	$59.10
Purchase #3	$204.74	8.840%	$222.839	$222.84	$222.85	$222.80
Purchase #4	$188.62	11.346%	$210.0208	$210.02	$210.00	$210.00
Purchase #5	$103.29	5.706%	$109.1837	$109.18	$109.20	$109.20
Purchase #6	$221.31	6.861%	$236.4941	$236.49	$236.50	$236.50
Purchase #7	$204.73	13.220%	$231.7953	$231.80	$231.80	$231.80
7 purchase totals =	$1,017.32		$1,116.7477	$1,116.74	$1,116.75	$1,116.70