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	$166.52	3.395%	$172.1734	$172.17	$172.15	$172.20
Purchase #2	$145.93	13.418%	$165.5109	$165.51	$165.50	$165.50
Purchase #3	$85.34	4.171%	$88.8995	$88.90	$88.90	$88.90
Purchase #4	$229.81	12.628%	$258.8304	$258.83	$258.85	$258.80
Purchase #5	$54.82	11.631%	$61.1961	$61.20	$61.20	$61.20
Purchase #6	$203.41	8.298%	$220.289	$220.29	$220.30	$220.30
Purchase #7	$178.71	12.870%	$201.71	$201.71	$201.70	$201.70
7 purchase totals =	$1,064.54		$1,168.6093	$1,168.61	$1,168.60	$1,168.60