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	$175.44	8.143%	$189.7261	$189.73	$189.75	$189.70
Purchase #2	$138.57	8.542%	$150.4066	$150.41	$150.40	$150.40
Purchase #3	$130.76	3.139%	$134.8646	$134.86	$134.85	$134.90
Purchase #4	$42.99	8.741%	$46.7478	$46.75	$46.75	$46.70
Purchase #5	$135.90	11.123%	$151.0162	$151.02	$151.00	$151.00
Purchase #6	$156.54	5.252%	$164.7615	$164.76	$164.75	$164.80
Purchase #7	$99.54	12.285%	$111.7685	$111.77	$111.75	$111.80
7 purchase totals =	$879.74		$949.2913	$949.30	$949.25	$949.30