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	$155.89	5.686%	$164.7539	$164.75	$164.75	$164.80
Purchase #2	$120.60	11.511%	$134.4823	$134.48	$134.50	$134.50
Purchase #3	$7.64	13.845%	$8.6978	$8.70	$8.70	$8.70
Purchase #4	$81.59	5.258%	$85.88	$85.88	$85.90	$85.90
Purchase #5	$226.51	9.329%	$247.6411	$247.64	$247.65	$247.60
Purchase #6	$99.52	4.612%	$104.1099	$104.11	$104.10	$104.10
Purchase #7	$120.41	9.513%	$131.8646	$131.86	$131.85	$131.90
7 purchase totals =	$812.16		$877.4296	$877.42	$877.45	$877.50