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	$207.33	9.315%	$226.6428	$226.64	$226.65	$226.60
Purchase #2	$34.70	7.232%	$37.2095	$37.21	$37.20	$37.20
Purchase #3	$195.43	13.747%	$222.2958	$222.30	$222.30	$222.30
Purchase #4	$25.33	9.612%	$27.7647	$27.76	$27.75	$27.80
Purchase #5	$167.92	13.338%	$190.3172	$190.32	$190.30	$190.30
Purchase #6	$214.63	5.243%	$225.8831	$225.88	$225.90	$225.90
Purchase #7	$122.97	10.827%	$136.284	$136.28	$136.30	$136.30
7 purchase totals =	$968.31		$1,066.3971	$1,066.39	$1,066.40	$1,066.40