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	$203.50	3.606%	$210.8382	$210.84	$210.85	$210.80
Purchase #2	$57.91	12.207%	$64.9791	$64.98	$65.00	$65.00
Purchase #3	$88.66	9.762%	$97.315	$97.32	$97.30	$97.30
Purchase #4	$119.32	12.350%	$134.056	$134.06	$134.05	$134.10
Purchase #5	$82.81	7.791%	$89.2617	$89.26	$89.25	$89.30
Purchase #6	$210.54	10.414%	$232.4656	$232.47	$232.45	$232.50
Purchase #7	$58.89	4.402%	$61.4823	$61.48	$61.50	$61.50
7 purchase totals =	$821.63		$890.3979	$890.41	$890.40	$890.50