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	$212.78	4.352%	$222.0402	$222.04	$222.05	$222.00
Purchase #2	$169.25	8.224%	$183.1691	$183.17	$183.15	$183.20
Purchase #3	$182.71	4.229%	$190.4368	$190.44	$190.45	$190.40
Purchase #4	$244.62	7.593%	$263.194	$263.19	$263.20	$263.20
Purchase #5	$91.29	9.177%	$99.6677	$99.67	$99.65	$99.70
Purchase #6	$248.83	4.343%	$259.6367	$259.64	$259.65	$259.60
Purchase #7	$35.38	4.835%	$37.0906	$37.09	$37.10	$37.10
7 purchase totals =	$1,184.86		$1,255.2351	$1,255.24	$1,255.25	$1,255.20