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	$200.61	11.528%	$223.7363	$223.74	$223.75	$223.70
Purchase #2	$59.67	13.826%	$67.92	$67.92	$67.90	$67.90
Purchase #3	$238.36	4.519%	$249.1315	$249.13	$249.15	$249.10
Purchase #4	$94.51	4.335%	$98.607	$98.61	$98.60	$98.60
Purchase #5	$31.59	7.297%	$33.8951	$33.90	$33.90	$33.90
Purchase #6	$114.89	7.421%	$123.416	$123.42	$123.40	$123.40
Purchase #7	$64.83	7.832%	$69.9075	$69.91	$69.90	$69.90
7 purchase totals =	$804.46		$866.6134	$866.63	$866.60	$866.50