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	$10.27	12.292%	$11.5324	$11.53	$11.55	$11.50
Purchase #2	$103.37	7.617%	$111.2437	$111.24	$111.25	$111.20
Purchase #3	$81.67	4.168%	$85.074	$85.07	$85.05	$85.10
Purchase #4	$23.87	3.827%	$24.7835	$24.78	$24.80	$24.80
Purchase #5	$147.48	3.140%	$152.1109	$152.11	$152.10	$152.10
Purchase #6	$152.93	11.831%	$171.0231	$171.02	$171.00	$171.00
Purchase #7	$228.57	7.817%	$246.4373	$246.44	$246.45	$246.40
7 purchase totals =	$748.16		$802.2049	$802.19	$802.20	$802.10