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	$63.98	8.518%	$69.4298	$69.43	$69.45	$69.40
Purchase #2	$18.39	6.156%	$19.5221	$19.52	$19.50	$19.50
Purchase #3	$186.44	5.220%	$196.1722	$196.17	$196.15	$196.20
Purchase #4	$107.44	8.395%	$116.4596	$116.46	$116.45	$116.50
Purchase #5	$100.33	9.188%	$109.5483	$109.55	$109.55	$109.50
Purchase #6	$68.61	3.727%	$71.1671	$71.17	$71.15	$71.20
Purchase #7	$147.44	12.778%	$166.2799	$166.28	$166.30	$166.30
7 purchase totals =	$692.63		$748.5790	$748.58	$748.55	$748.60