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	$87.51	4.768%	$91.6825	$91.68	$91.70	$91.70
Purchase #2	$121.88	4.460%	$127.3158	$127.32	$127.30	$127.30
Purchase #3	$110.65	12.169%	$124.115	$124.12	$124.10	$124.10
Purchase #4	$6.36	5.839%	$6.7314	$6.73	$6.75	$6.70
Purchase #5	$171.33	9.425%	$187.4779	$187.48	$187.50	$187.50
Purchase #6	$33.47	6.169%	$35.5348	$35.53	$35.55	$35.50
Purchase #7	$56.41	5.771%	$59.6654	$59.67	$59.65	$59.70
7 purchase totals =	$587.61		$632.5228	$632.53	$632.55	$632.50