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	$192.55	3.541%	$199.3682	$199.37	$199.35	$199.40
Purchase #2	$27.69	6.654%	$29.5325	$29.53	$29.55	$29.50
Purchase #3	$91.60	11.519%	$102.1514	$102.15	$102.15	$102.20
Purchase #4	$156.80	5.385%	$165.2437	$165.24	$165.25	$165.20
Purchase #5	$171.65	7.143%	$183.911	$183.91	$183.90	$183.90
Purchase #6	$65.45	9.824%	$71.8798	$71.88	$71.90	$71.90
Purchase #7	$139.66	7.653%	$150.3482	$150.35	$150.35	$150.30
7 purchase totals =	$845.40		$902.4348	$902.43	$902.45	$902.40