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	$48.50	9.813%	$53.2593	$53.26	$53.25	$53.30
Purchase #2	$82.61	8.109%	$89.3088	$89.31	$89.30	$89.30
Purchase #3	$111.28	3.628%	$115.3172	$115.32	$115.30	$115.30
Purchase #4	$200.50	5.820%	$212.1691	$212.17	$212.15	$212.20
Purchase #5	$192.99	6.451%	$205.4398	$205.44	$205.45	$205.40
Purchase #6	$215.48	11.746%	$240.7903	$240.79	$240.80	$240.80
Purchase #7	$22.29	11.380%	$24.8266	$24.83	$24.85	$24.80
7 purchase totals =	$873.65		$941.1111	$941.12	$941.10	$941.10