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	$197.86	9.304%	$216.2689	$216.27	$216.25	$216.30
Purchase #2	$104.74	8.178%	$113.3056	$113.31	$113.30	$113.30
Purchase #3	$142.62	12.505%	$160.4546	$160.45	$160.45	$160.50
Purchase #4	$25.97	9.793%	$28.5132	$28.51	$28.50	$28.50
Purchase #5	$77.72	11.667%	$86.7876	$86.79	$86.80	$86.80
Purchase #6	$214.28	4.190%	$223.2583	$223.26	$223.25	$223.30
Purchase #7	$116.97	5.542%	$123.4525	$123.45	$123.45	$123.50
7 purchase totals =	$880.16		$952.0407	$952.04	$952.00	$952.20