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	$106.53	7.384%	$114.3962	$114.40	$114.40	$114.40
Purchase #2	$34.83	8.720%	$37.8672	$37.87	$37.85	$37.90
Purchase #3	$33.97	11.551%	$37.8939	$37.89	$37.90	$37.90
Purchase #4	$218.91	12.146%	$245.4988	$245.50	$245.50	$245.50
Purchase #5	$59.63	5.511%	$62.9162	$62.92	$62.90	$62.90
Purchase #6	$106.81	6.117%	$113.3436	$113.34	$113.35	$113.30
Purchase #7	$159.41	8.198%	$172.4784	$172.48	$172.50	$172.50
7 purchase totals =	$720.09		$784.3943	$784.40	$784.40	$784.40