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	$208.53	6.488%	$222.0594	$222.06	$222.05	$222.10
Purchase #2	$110.43	4.870%	$115.8079	$115.81	$115.80	$115.80
Purchase #3	$20.56	3.113%	$21.2	$21.20	$21.20	$21.20
Purchase #4	$61.75	3.501%	$63.9119	$63.91	$63.90	$63.90
Purchase #5	$80.30	3.848%	$83.3899	$83.39	$83.40	$83.40
Purchase #6	$38.89	12.157%	$43.6179	$43.62	$43.60	$43.60
Purchase #7	$234.78	5.753%	$248.2869	$248.29	$248.30	$248.30
7 purchase totals =	$755.24		$798.2739	$798.28	$798.25	$798.30