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	$213.29	13.510%	$242.1055	$242.11	$242.10	$242.10
Purchase #2	$124.84	11.710%	$139.4588	$139.46	$139.45	$139.50
Purchase #3	$187.34	13.818%	$213.2266	$213.23	$213.25	$213.20
Purchase #4	$186.87	10.440%	$206.3792	$206.38	$206.40	$206.40
Purchase #5	$95.48	4.611%	$99.8826	$99.88	$99.90	$99.90
Purchase #6	$223.69	10.681%	$247.5823	$247.58	$247.60	$247.60
Purchase #7	$139.88	7.565%	$150.4619	$150.46	$150.45	$150.50
7 purchase totals =	$1,171.39		$1,299.0969	$1,299.10	$1,299.15	$1,299.20