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	$168.92	10.105%	$185.9894	$185.99	$186.00	$186.00
Purchase #2	$12.29	4.604%	$12.8558	$12.86	$12.85	$12.90
Purchase #3	$120.68	4.319%	$125.8922	$125.89	$125.90	$125.90
Purchase #4	$235.54	12.204%	$264.2853	$264.29	$264.30	$264.30
Purchase #5	$245.43	8.218%	$265.5994	$265.60	$265.60	$265.60
Purchase #6	$179.79	6.346%	$191.1995	$191.20	$191.20	$191.20
Purchase #7	$80.87	6.128%	$85.8257	$85.83	$85.85	$85.80
7 purchase totals =	$1,043.52		$1,131.6473	$1,131.66	$1,131.70	$1,131.70