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	$208.52	12.638%	$234.8728	$234.87	$234.85	$234.90
Purchase #2	$67.58	4.855%	$70.861	$70.86	$70.85	$70.90
Purchase #3	$49.44	11.399%	$55.0757	$55.08	$55.10	$55.10
Purchase #4	$76.78	7.227%	$82.3289	$82.33	$82.35	$82.30
Purchase #5	$148.25	11.581%	$165.4188	$165.42	$165.40	$165.40
Purchase #6	$243.63	8.460%	$264.2411	$264.24	$264.25	$264.20
Purchase #7	$54.56	5.618%	$57.6252	$57.63	$57.65	$57.60
7 purchase totals =	$848.76		$930.4235	$930.43	$930.45	$930.40