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	$43.74	3.471%	$45.2582	$45.26	$45.25	$45.30
Purchase #2	$172.94	11.758%	$193.2743	$193.27	$193.25	$193.30
Purchase #3	$149.32	12.726%	$168.3225	$168.32	$168.30	$168.30
Purchase #4	$156.59	6.814%	$167.26	$167.26	$167.25	$167.30
Purchase #5	$31.59	12.763%	$35.6218	$35.62	$35.60	$35.60
Purchase #6	$124.39	11.126%	$138.2296	$138.23	$138.25	$138.20
Purchase #7	$78.51	13.359%	$88.9982	$89.00	$89.00	$89.00
7 purchase totals =	$757.08		$836.9646	$836.96	$836.90	$837.00