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	$176.25	5.430%	$185.8204	$185.82	$185.80	$185.80
Purchase #2	$57.31	3.608%	$59.3777	$59.38	$59.40	$59.40
Purchase #3	$151.49	4.195%	$157.845	$157.85	$157.85	$157.80
Purchase #4	$75.41	10.229%	$83.1237	$83.12	$83.10	$83.10
Purchase #5	$80.28	6.445%	$85.454	$85.45	$85.45	$85.50
Purchase #6	$102.25	6.196%	$108.5854	$108.59	$108.60	$108.60
Purchase #7	$213.88	7.494%	$229.9082	$229.91	$229.90	$229.90
7 purchase totals =	$856.87		$910.1144	$910.12	$910.10	$910.10