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	$85.53	6.189%	$90.8235	$90.82	$90.80	$90.80
Purchase #2	$152.74	6.477%	$162.633	$162.63	$162.65	$162.60
Purchase #3	$32.98	8.836%	$35.8941	$35.89	$35.90	$35.90
Purchase #4	$225.69	12.661%	$254.2646	$254.26	$254.25	$254.30
Purchase #5	$47.99	3.664%	$49.7484	$49.75	$49.75	$49.70
Purchase #6	$110.29	6.360%	$117.3044	$117.30	$117.30	$117.30
Purchase #7	$43.30	7.441%	$46.522	$46.52	$46.50	$46.50
7 purchase totals =	$698.52		$757.1900	$757.17	$757.15	$757.10