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	$173.31	13.429%	$196.5838	$196.58	$196.60	$196.60
Purchase #2	$34.62	3.674%	$35.8919	$35.89	$35.90	$35.90
Purchase #3	$210.93	5.794%	$223.1513	$223.15	$223.15	$223.20
Purchase #4	$245.98	12.370%	$276.4077	$276.41	$276.40	$276.40
Purchase #5	$187.79	3.112%	$193.634	$193.63	$193.65	$193.60
Purchase #6	$141.75	11.493%	$158.0413	$158.04	$158.05	$158.00
Purchase #7	$24.99	13.743%	$28.4244	$28.42	$28.40	$28.40
7 purchase totals =	$1,019.37		$1,112.1344	$1,112.12	$1,112.15	$1,112.10