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	$217.69	13.423%	$246.9105	$246.91	$246.90	$246.90
Purchase #2	$50.25	7.516%	$54.0268	$54.03	$54.05	$54.00
Purchase #3	$136.51	8.471%	$148.0738	$148.07	$148.05	$148.10
Purchase #4	$88.81	12.526%	$99.9343	$99.93	$99.95	$99.90
Purchase #5	$100.56	6.690%	$107.2875	$107.29	$107.30	$107.30
Purchase #6	$77.68	6.432%	$82.6764	$82.68	$82.70	$82.70
Purchase #7	$140.33	8.607%	$152.4082	$152.41	$152.40	$152.40
7 purchase totals =	$811.83		$891.3175	$891.32	$891.35	$891.30