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	$234.42	4.788%	$245.644	$245.64	$245.65	$245.60
Purchase #2	$18.72	6.502%	$19.9372	$19.94	$19.95	$19.90
Purchase #3	$92.87	4.426%	$96.9804	$96.98	$97.00	$97.00
Purchase #4	$144.31	7.731%	$155.4666	$155.47	$155.45	$155.50
Purchase #5	$137.69	6.731%	$146.9579	$146.96	$146.95	$147.00
Purchase #6	$250.86	9.572%	$274.8723	$274.87	$274.85	$274.90
Purchase #7	$79.43	11.365%	$88.4572	$88.46	$88.45	$88.50
7 purchase totals =	$958.30		$1,028.3156	$1,028.32	$1,028.30	$1,028.40