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	$205.33	6.313%	$218.2925	$218.29	$218.30	$218.30
Purchase #2	$183.94	10.414%	$203.0955	$203.10	$203.10	$203.10
Purchase #3	$173.32	6.498%	$184.5823	$184.58	$184.60	$184.60
Purchase #4	$78.90	13.835%	$89.8158	$89.82	$89.80	$89.80
Purchase #5	$242.39	13.461%	$275.0181	$275.02	$275.00	$275.00
Purchase #6	$99.39	7.184%	$106.5302	$106.53	$106.55	$106.50
Purchase #7	$30.85	3.301%	$31.8684	$31.87	$31.85	$31.90
7 purchase totals =	$1,014.12		$1,109.2028	$1,109.21	$1,109.20	$1,109.20