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	$115.87	10.236%	$127.7305	$127.73	$127.75	$127.70
Purchase #2	$85.92	4.323%	$89.6343	$89.63	$89.65	$89.60
Purchase #3	$221.57	4.507%	$231.5562	$231.56	$231.55	$231.60
Purchase #4	$208.71	12.289%	$234.3584	$234.36	$234.35	$234.40
Purchase #5	$109.98	13.734%	$125.0847	$125.08	$125.10	$125.10
Purchase #6	$100.27	8.165%	$108.457	$108.46	$108.45	$108.50
Purchase #7	$49.43	9.711%	$54.2301	$54.23	$54.25	$54.20
7 purchase totals =	$891.75		$971.0512	$971.05	$971.10	$971.10