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	$202.96	3.269%	$209.5948	$209.59	$209.60	$209.60
Purchase #2	$66.55	9.511%	$72.8796	$72.88	$72.90	$72.90
Purchase #3	$228.28	7.103%	$244.4947	$244.49	$244.50	$244.50
Purchase #4	$57.90	3.673%	$60.0267	$60.03	$60.05	$60.00
Purchase #5	$9.84	10.568%	$10.8799	$10.88	$10.90	$10.90
Purchase #6	$231.28	3.230%	$238.7503	$238.75	$238.75	$238.80
Purchase #7	$229.56	11.251%	$255.3878	$255.39	$255.40	$255.40
7 purchase totals =	$1,026.37		$1,092.0138	$1,092.01	$1,092.10	$1,092.10