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	$111.35	9.420%	$121.8392	$121.84	$121.85	$121.80
Purchase #2	$46.58	13.536%	$52.8851	$52.89	$52.90	$52.90
Purchase #3	$53.98	3.809%	$56.0361	$56.04	$56.05	$56.00
Purchase #4	$204.71	11.124%	$227.4819	$227.48	$227.50	$227.50
Purchase #5	$128.36	3.868%	$133.325	$133.33	$133.35	$133.30
Purchase #6	$30.69	3.372%	$31.7249	$31.72	$31.70	$31.70
Purchase #7	$185.73	5.794%	$196.4912	$196.49	$196.50	$196.50
7 purchase totals =	$761.40		$819.7834	$819.79	$819.85	$819.70