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	$81.71	5.430%	$86.1469	$86.15	$86.15	$86.10
Purchase #2	$235.70	8.658%	$256.1069	$256.11	$256.10	$256.10
Purchase #3	$172.42	6.864%	$184.2549	$184.25	$184.25	$184.30
Purchase #4	$27.63	6.650%	$29.4674	$29.47	$29.45	$29.50
Purchase #5	$165.47	4.696%	$173.2405	$173.24	$173.25	$173.20
Purchase #6	$18.57	12.310%	$20.856	$20.86	$20.85	$20.90
Purchase #7	$38.36	8.117%	$41.4737	$41.47	$41.45	$41.50
7 purchase totals =	$739.86		$791.5463	$791.55	$791.50	$791.60