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	$99.37	4.848%	$104.1875	$104.19	$104.20	$104.20
Purchase #2	$152.91	13.652%	$173.7853	$173.79	$173.80	$173.80
Purchase #3	$80.49	5.839%	$85.1898	$85.19	$85.20	$85.20
Purchase #4	$36.72	13.670%	$41.7396	$41.74	$41.75	$41.70
Purchase #5	$74.81	9.389%	$81.8339	$81.83	$81.85	$81.80
Purchase #6	$213.43	4.771%	$223.6127	$223.61	$223.60	$223.60
Purchase #7	$165.79	11.701%	$185.1891	$185.19	$185.20	$185.20
7 purchase totals =	$823.52		$895.5379	$895.54	$895.60	$895.50