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	$200.70	9.545%	$219.8568	$219.86	$219.85	$219.90
Purchase #2	$158.85	3.386%	$164.2287	$164.23	$164.25	$164.20
Purchase #3	$248.42	10.117%	$273.5527	$273.55	$273.55	$273.60
Purchase #4	$33.44	6.220%	$35.52	$35.52	$35.50	$35.50
Purchase #5	$148.65	12.584%	$167.3561	$167.36	$167.35	$167.40
Purchase #6	$26.52	12.114%	$29.7326	$29.73	$29.75	$29.70
Purchase #7	$162.74	8.519%	$176.6038	$176.60	$176.60	$176.60
7 purchase totals =	$979.32		$1,066.8507	$1,066.85	$1,066.85	$1,066.90