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	$147.97	5.593%	$156.246	$156.25	$156.25	$156.20
Purchase #2	$103.67	7.440%	$111.383	$111.38	$111.40	$111.40
Purchase #3	$203.55	6.237%	$216.2454	$216.25	$216.25	$216.20
Purchase #4	$200.77	5.843%	$212.501	$212.50	$212.50	$212.50
Purchase #5	$102.87	11.762%	$114.9696	$114.97	$114.95	$115.00
Purchase #6	$70.96	13.323%	$80.414	$80.41	$80.40	$80.40
Purchase #7	$222.34	11.764%	$248.4961	$248.50	$248.50	$248.50
7 purchase totals =	$1,052.13		$1,140.2551	$1,140.26	$1,140.25	$1,140.20