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	$85.34	8.365%	$92.4787	$92.48	$92.50	$92.50
Purchase #2	$90.90	5.318%	$95.7341	$95.73	$95.75	$95.70
Purchase #3	$29.72	9.821%	$32.6388	$32.64	$32.65	$32.60
Purchase #4	$164.56	13.488%	$186.7559	$186.76	$186.75	$186.80
Purchase #5	$39.41	12.658%	$44.3985	$44.40	$44.40	$44.40
Purchase #6	$175.40	5.170%	$184.4682	$184.47	$184.45	$184.50
Purchase #7	$137.42	10.345%	$151.6361	$151.64	$151.65	$151.60
7 purchase totals =	$722.75		$788.1103	$788.12	$788.15	$788.10