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	$124.60	5.111%	$130.9683	$130.97	$130.95	$131.00
Purchase #2	$139.73	11.784%	$156.1958	$156.20	$156.20	$156.20
Purchase #3	$200.38	12.326%	$225.0788	$225.08	$225.10	$225.10
Purchase #4	$63.54	13.868%	$72.3517	$72.35	$72.35	$72.40
Purchase #5	$23.38	8.550%	$25.379	$25.38	$25.40	$25.40
Purchase #6	$30.29	11.774%	$33.8563	$33.86	$33.85	$33.90
Purchase #7	$212.41	6.138%	$225.4477	$225.45	$225.45	$225.40
7 purchase totals =	$794.33		$869.2776	$869.29	$869.30	$869.40