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	$80.80	7.494%	$86.8552	$86.86	$86.85	$86.90
Purchase #2	$244.61	4.742%	$256.2094	$256.21	$256.20	$256.20
Purchase #3	$54.63	13.709%	$62.1192	$62.12	$62.10	$62.10
Purchase #4	$231.95	4.559%	$242.5246	$242.52	$242.50	$242.50
Purchase #5	$111.60	7.367%	$119.8216	$119.82	$119.80	$119.80
Purchase #6	$114.51	9.393%	$125.2659	$125.27	$125.25	$125.30
Purchase #7	$172.30	10.563%	$190.5	$190.50	$190.50	$190.50
7 purchase totals =	$1,010.40		$1,083.2959	$1,083.30	$1,083.20	$1,083.30