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	$100.78	7.401%	$108.2387	$108.24	$108.25	$108.20
Purchase #2	$197.59	11.792%	$220.8898	$220.89	$220.90	$220.90
Purchase #3	$152.54	6.346%	$162.2202	$162.22	$162.20	$162.20
Purchase #4	$95.81	4.330%	$99.9586	$99.96	$99.95	$100.00
Purchase #5	$197.71	13.269%	$223.9441	$223.94	$223.95	$223.90
Purchase #6	$31.90	12.567%	$35.9089	$35.91	$35.90	$35.90
Purchase #7	$233.73	8.819%	$254.3426	$254.34	$254.35	$254.30
7 purchase totals =	$1,010.06		$1,105.5029	$1,105.50	$1,105.50	$1,105.40