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	$216.66	12.103%	$242.8824	$242.88	$242.90	$242.90
Purchase #2	$165.47	5.809%	$175.0822	$175.08	$175.10	$175.10
Purchase #3	$184.35	6.811%	$196.9061	$196.91	$196.90	$196.90
Purchase #4	$139.93	13.203%	$158.405	$158.41	$158.40	$158.40
Purchase #5	$161.83	11.143%	$179.8627	$179.86	$179.85	$179.90
Purchase #6	$88.90	13.412%	$100.8233	$100.82	$100.80	$100.80
Purchase #7	$155.52	9.539%	$170.3551	$170.36	$170.35	$170.40
7 purchase totals =	$1,112.66		$1,224.3168	$1,224.32	$1,224.30	$1,224.40