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	$49.43	8.426%	$53.595	$53.60	$53.60	$53.60
Purchase #2	$66.67	11.513%	$74.3457	$74.35	$74.35	$74.30
Purchase #3	$50.90	4.564%	$53.2231	$53.22	$53.20	$53.20
Purchase #4	$225.31	8.815%	$245.1711	$245.17	$245.15	$245.20
Purchase #5	$37.65	4.456%	$39.3277	$39.33	$39.35	$39.30
Purchase #6	$228.54	11.606%	$255.0644	$255.06	$255.05	$255.10
Purchase #7	$6.80	7.440%	$7.3059	$7.31	$7.30	$7.30
7 purchase totals =	$665.30		$728.0329	$728.04	$728.00	$728.00