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	$173.75	4.432%	$181.4506	$181.45	$181.45	$181.50
Purchase #2	$217.98	11.275%	$242.5572	$242.56	$242.55	$242.60
Purchase #3	$36.66	10.775%	$40.6101	$40.61	$40.60	$40.60
Purchase #4	$39.85	13.339%	$45.1656	$45.17	$45.15	$45.20
Purchase #5	$249.65	13.118%	$282.3991	$282.40	$282.40	$282.40
Purchase #6	$63.60	8.770%	$69.1777	$69.18	$69.20	$69.20
Purchase #7	$168.39	12.227%	$188.979	$188.98	$189.00	$189.00
7 purchase totals =	$949.88		$1,050.3393	$1,050.35	$1,050.35	$1,050.50