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	$205.89	10.761%	$228.0458	$228.05	$228.05	$228.00
Purchase #2	$98.71	6.666%	$105.29	$105.29	$105.30	$105.30
Purchase #3	$111.87	6.164%	$118.7657	$118.77	$118.75	$118.80
Purchase #4	$242.84	8.791%	$264.1881	$264.19	$264.20	$264.20
Purchase #5	$200.31	5.110%	$210.5458	$210.55	$210.55	$210.50
Purchase #6	$19.90	5.782%	$21.0506	$21.05	$21.05	$21.10
Purchase #7	$172.90	10.716%	$191.428	$191.43	$191.45	$191.40
7 purchase totals =	$1,052.42		$1,139.3140	$1,139.33	$1,139.35	$1,139.30