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	$119.27	9.725%	$130.869	$130.87	$130.85	$130.90
Purchase #2	$31.46	3.676%	$32.6165	$32.62	$32.60	$32.60
Purchase #3	$146.81	10.608%	$162.3836	$162.38	$162.40	$162.40
Purchase #4	$215.62	10.567%	$238.4046	$238.40	$238.40	$238.40
Purchase #5	$100.39	13.288%	$113.7298	$113.73	$113.75	$113.70
Purchase #6	$27.73	13.582%	$31.4963	$31.50	$31.50	$31.50
Purchase #7	$247.41	9.346%	$270.5329	$270.53	$270.55	$270.50
7 purchase totals =	$888.69		$980.0327	$980.03	$980.05	$980.00