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	$61.60	4.410%	$64.3166	$64.32	$64.30	$64.30
Purchase #2	$91.73	3.577%	$95.0112	$95.01	$95.00	$95.00
Purchase #3	$56.84	13.760%	$64.6612	$64.66	$64.65	$64.70
Purchase #4	$34.75	8.675%	$37.7646	$37.76	$37.75	$37.80
Purchase #5	$75.55	4.432%	$78.8984	$78.90	$78.90	$78.90
Purchase #6	$103.32	8.493%	$112.095	$112.10	$112.10	$112.10
Purchase #7	$99.81	4.201%	$104.003	$104.00	$104.00	$104.00
7 purchase totals =	$523.60		$556.7500	$556.75	$556.70	$556.80