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	$243.25	3.784%	$252.4546	$252.45	$252.45	$252.50
Purchase #2	$172.97	10.390%	$190.9416	$190.94	$190.95	$190.90
Purchase #3	$85.27	5.107%	$89.6247	$89.62	$89.60	$89.60
Purchase #4	$218.74	7.749%	$235.6902	$235.69	$235.70	$235.70
Purchase #5	$27.79	13.142%	$31.4422	$31.44	$31.45	$31.40
Purchase #6	$141.91	9.416%	$155.2722	$155.27	$155.25	$155.30
Purchase #7	$73.86	6.679%	$78.7931	$78.79	$78.80	$78.80
7 purchase totals =	$963.79		$1,034.2186	$1,034.20	$1,034.20	$1,034.20