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	$177.54	8.775%	$193.1191	$193.12	$193.10	$193.10
Purchase #2	$170.76	8.241%	$184.8323	$184.83	$184.85	$184.80
Purchase #3	$200.36	13.765%	$227.9396	$227.94	$227.95	$227.90
Purchase #4	$172.56	3.606%	$178.7825	$178.78	$178.80	$178.80
Purchase #5	$105.47	6.452%	$112.2749	$112.27	$112.25	$112.30
Purchase #6	$80.38	10.156%	$88.5434	$88.54	$88.55	$88.50
Purchase #7	$146.79	12.846%	$165.6466	$165.65	$165.65	$165.60
7 purchase totals =	$1,053.86		$1,151.1384	$1,151.13	$1,151.15	$1,151.00