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	$219.32	8.658%	$238.3087	$238.31	$238.30	$238.30
Purchase #2	$108.77	6.827%	$116.1957	$116.20	$116.20	$116.20
Purchase #3	$128.91	6.533%	$137.3317	$137.33	$137.35	$137.30
Purchase #4	$19.31	3.364%	$19.9596	$19.96	$19.95	$20.00
Purchase #5	$169.49	8.771%	$184.356	$184.36	$184.35	$184.40
Purchase #6	$211.59	5.320%	$222.8466	$222.85	$222.85	$222.80
Purchase #7	$139.48	11.467%	$155.4742	$155.47	$155.45	$155.50
7 purchase totals =	$996.87		$1,074.4725	$1,074.48	$1,074.45	$1,074.50