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	$155.59	12.497%	$175.0341	$175.03	$175.05	$175.00
Purchase #2	$29.89	13.456%	$33.912	$33.91	$33.90	$33.90
Purchase #3	$85.39	11.286%	$95.0271	$95.03	$95.05	$95.00
Purchase #4	$144.57	8.435%	$156.7645	$156.76	$156.75	$156.80
Purchase #5	$29.78	6.155%	$31.613	$31.61	$31.60	$31.60
Purchase #6	$173.33	5.652%	$183.1266	$183.13	$183.15	$183.10
Purchase #7	$84.61	9.272%	$92.455	$92.46	$92.45	$92.50
7 purchase totals =	$703.16		$767.9323	$767.93	$767.95	$767.90