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	$58.38	4.726%	$61.139	$61.14	$61.15	$61.10
Purchase #2	$75.49	6.135%	$80.1213	$80.12	$80.10	$80.10
Purchase #3	$33.31	6.639%	$35.5215	$35.52	$35.50	$35.50
Purchase #4	$104.95	12.552%	$118.1233	$118.12	$118.10	$118.10
Purchase #5	$59.33	10.691%	$65.673	$65.67	$65.65	$65.70
Purchase #6	$125.67	12.618%	$141.527	$141.53	$141.55	$141.50
Purchase #7	$145.40	6.500%	$154.851	$154.85	$154.85	$154.90
7 purchase totals =	$602.53		$656.9561	$656.95	$656.90	$656.90