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	$91.71	4.593%	$95.9222	$95.92	$95.90	$95.90
Purchase #2	$212.67	12.786%	$239.862	$239.86	$239.85	$239.90
Purchase #3	$32.83	13.517%	$37.2676	$37.27	$37.25	$37.30
Purchase #4	$27.64	6.288%	$29.378	$29.38	$29.40	$29.40
Purchase #5	$36.30	3.323%	$37.5062	$37.51	$37.50	$37.50
Purchase #6	$147.50	3.252%	$152.2967	$152.30	$152.30	$152.30
Purchase #7	$48.41	7.667%	$52.1216	$52.12	$52.10	$52.10
7 purchase totals =	$597.06		$644.3543	$644.36	$644.30	$644.40