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	$240.53	6.541%	$256.2631	$256.26	$256.25	$256.30
Purchase #2	$79.53	12.128%	$89.1754	$89.18	$89.20	$89.20
Purchase #3	$185.80	3.283%	$191.8998	$191.90	$191.90	$191.90
Purchase #4	$126.90	3.600%	$131.4684	$131.47	$131.45	$131.50
Purchase #5	$42.96	12.418%	$48.2948	$48.29	$48.30	$48.30
Purchase #6	$130.52	12.345%	$146.6327	$146.63	$146.65	$146.60
Purchase #7	$191.80	9.607%	$210.2262	$210.23	$210.25	$210.20
7 purchase totals =	$998.04		$1,073.9604	$1,073.96	$1,074.00	$1,074.00