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	$56.38	4.318%	$58.8145	$58.81	$58.80	$58.80
Purchase #2	$16.70	11.220%	$18.5737	$18.57	$18.55	$18.60
Purchase #3	$13.83	10.595%	$15.2953	$15.30	$15.30	$15.30
Purchase #4	$234.69	6.638%	$250.2687	$250.27	$250.25	$250.30
Purchase #5	$110.76	11.244%	$123.2139	$123.21	$123.20	$123.20
Purchase #6	$175.44	7.760%	$189.0541	$189.05	$189.05	$189.10
Purchase #7	$79.43	12.421%	$89.296	$89.30	$89.30	$89.30
7 purchase totals =	$687.23		$744.5162	$744.51	$744.45	$744.60