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	$33.44	3.644%	$34.6586	$34.66	$34.65	$34.70
Purchase #2	$156.35	6.834%	$167.035	$167.04	$167.05	$167.00
Purchase #3	$51.56	5.854%	$54.5783	$54.58	$54.60	$54.60
Purchase #4	$14.67	4.446%	$15.3222	$15.32	$15.30	$15.30
Purchase #5	$50.28	4.315%	$52.4496	$52.45	$52.45	$52.40
Purchase #6	$61.71	5.788%	$65.2818	$65.28	$65.30	$65.30
Purchase #7	$96.79	8.618%	$105.1314	$105.13	$105.15	$105.10
7 purchase totals =	$464.80		$494.4569	$494.46	$494.50	$494.40