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	$196.47	6.869%	$209.9655	$209.97	$209.95	$210.00
Purchase #2	$90.38	12.214%	$101.419	$101.42	$101.40	$101.40
Purchase #3	$122.50	5.839%	$129.6528	$129.65	$129.65	$129.70
Purchase #4	$59.54	13.695%	$67.694	$67.69	$67.70	$67.70
Purchase #5	$114.65	11.455%	$127.7832	$127.78	$127.80	$127.80
Purchase #6	$28.78	8.351%	$31.1834	$31.18	$31.20	$31.20
Purchase #7	$69.46	3.672%	$72.0106	$72.01	$72.00	$72.00
7 purchase totals =	$681.78		$739.7085	$739.70	$739.70	$739.80