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	$152.53	8.585%	$165.6247	$165.62	$165.60	$165.60
Purchase #2	$80.84	10.782%	$89.5562	$89.56	$89.55	$89.60
Purchase #3	$31.28	13.477%	$35.4956	$35.50	$35.50	$35.50
Purchase #4	$146.70	13.715%	$166.8199	$166.82	$166.80	$166.80
Purchase #5	$225.52	12.697%	$254.1543	$254.15	$254.15	$254.20
Purchase #6	$119.72	12.414%	$134.582	$134.58	$134.60	$134.60
Purchase #7	$139.45	13.874%	$158.7973	$158.80	$158.80	$158.80
7 purchase totals =	$896.04		$1,005.0300	$1,005.03	$1,005.00	$1,005.10