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	$68.58	8.234%	$74.2269	$74.23	$74.25	$74.20
Purchase #2	$155.94	10.460%	$172.2513	$172.25	$172.25	$172.30
Purchase #3	$221.83	7.650%	$238.8	$238.80	$238.80	$238.80
Purchase #4	$59.79	7.207%	$64.0991	$64.10	$64.10	$64.10
Purchase #5	$39.33	10.542%	$43.4762	$43.48	$43.50	$43.50
Purchase #6	$48.63	13.646%	$55.266	$55.27	$55.25	$55.30
Purchase #7	$29.83	11.690%	$33.3171	$33.32	$33.30	$33.30
7 purchase totals =	$623.93		$681.4366	$681.45	$681.45	$681.50