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	$226.37	4.595%	$236.7717	$236.77	$236.75	$236.80
Purchase #2	$79.76	7.485%	$85.73	$85.73	$85.75	$85.70
Purchase #3	$248.87	6.730%	$265.619	$265.62	$265.60	$265.60
Purchase #4	$67.63	4.401%	$70.6064	$70.61	$70.60	$70.60
Purchase #5	$113.70	12.482%	$127.892	$127.89	$127.90	$127.90
Purchase #6	$175.25	8.142%	$189.5189	$189.52	$189.50	$189.50
Purchase #7	$69.70	5.226%	$73.3425	$73.34	$73.35	$73.30
7 purchase totals =	$981.28		$1,049.4805	$1,049.48	$1,049.45	$1,049.40