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	$142.56	6.268%	$151.4957	$151.50	$151.50	$151.50
Purchase #2	$169.70	8.114%	$183.4695	$183.47	$183.45	$183.50
Purchase #3	$38.28	4.562%	$40.0263	$40.03	$40.05	$40.00
Purchase #4	$69.70	12.320%	$78.287	$78.29	$78.30	$78.30
Purchase #5	$151.32	7.133%	$162.1137	$162.11	$162.10	$162.10
Purchase #6	$15.83	5.588%	$16.7146	$16.71	$16.70	$16.70
Purchase #7	$142.62	5.799%	$150.8905	$150.89	$150.90	$150.90
7 purchase totals =	$730.01		$782.9973	$783.00	$783.00	$783.00