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	$61.31	6.203%	$65.1131	$65.11	$65.10	$65.10
Purchase #2	$56.37	8.386%	$61.0972	$61.10	$61.10	$61.10
Purchase #3	$99.91	11.108%	$111.008	$111.01	$111.00	$111.00
Purchase #4	$48.80	8.257%	$52.8294	$52.83	$52.85	$52.80
Purchase #5	$109.61	3.869%	$113.8508	$113.85	$113.85	$113.90
Purchase #6	$188.62	3.255%	$194.7596	$194.76	$194.75	$194.80
Purchase #7	$104.56	7.601%	$112.5076	$112.51	$112.50	$112.50
7 purchase totals =	$669.18		$711.1657	$711.17	$711.15	$711.20