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	$41.44	3.507%	$42.8933	$42.89	$42.90	$42.90
Purchase #2	$111.78	4.807%	$117.1533	$117.15	$117.15	$117.20
Purchase #3	$213.75	4.417%	$223.1913	$223.19	$223.20	$223.20
Purchase #4	$213.36	10.356%	$235.4556	$235.46	$235.45	$235.50
Purchase #5	$33.89	11.847%	$37.9049	$37.90	$37.90	$37.90
Purchase #6	$127.97	7.574%	$137.6624	$137.66	$137.65	$137.70
Purchase #7	$241.42	11.775%	$269.8472	$269.85	$269.85	$269.80
7 purchase totals =	$983.61		$1,064.1080	$1,064.10	$1,064.10	$1,064.20