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	$172.65	13.773%	$196.4291	$196.43	$196.45	$196.40
Purchase #2	$6.85	6.280%	$7.2802	$7.28	$7.30	$7.30
Purchase #3	$106.88	11.826%	$119.5196	$119.52	$119.50	$119.50
Purchase #4	$209.63	11.791%	$234.3475	$234.35	$234.35	$234.30
Purchase #5	$44.77	5.496%	$47.2306	$47.23	$47.25	$47.20
Purchase #6	$129.33	7.795%	$139.4113	$139.41	$139.40	$139.40
Purchase #7	$76.75	5.155%	$80.7065	$80.71	$80.70	$80.70
7 purchase totals =	$746.86		$824.9248	$824.93	$824.95	$824.80