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	$36.89	3.714%	$38.2601	$38.26	$38.25	$38.30
Purchase #2	$132.56	6.447%	$141.1061	$141.11	$141.10	$141.10
Purchase #3	$69.82	13.395%	$79.1724	$79.17	$79.15	$79.20
Purchase #4	$27.29	3.592%	$28.2703	$28.27	$28.25	$28.30
Purchase #5	$123.55	3.103%	$127.3838	$127.38	$127.40	$127.40
Purchase #6	$124.70	3.618%	$129.2116	$129.21	$129.20	$129.20
Purchase #7	$19.78	5.702%	$20.9079	$20.91	$20.90	$20.90
7 purchase totals =	$534.59		$564.3122	$564.31	$564.25	$564.40