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	$32.79	3.732%	$34.0137	$34.01	$34.00	$34.00
Purchase #2	$28.33	11.245%	$31.5157	$31.52	$31.50	$31.50
Purchase #3	$91.69	7.476%	$98.5447	$98.54	$98.55	$98.50
Purchase #4	$65.51	10.104%	$72.1291	$72.13	$72.15	$72.10
Purchase #5	$159.41	5.289%	$167.8412	$167.84	$167.85	$167.80
Purchase #6	$93.84	6.232%	$99.6881	$99.69	$99.70	$99.70
Purchase #7	$186.25	9.401%	$203.7594	$203.76	$203.75	$203.80
7 purchase totals =	$657.82		$707.4919	$707.49	$707.50	$707.40