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	$195.73	5.229%	$205.9647	$205.96	$205.95	$206.00
Purchase #2	$31.49	13.670%	$35.7947	$35.79	$35.80	$35.80
Purchase #3	$165.73	4.536%	$173.2475	$173.25	$173.25	$173.20
Purchase #4	$71.61	9.301%	$78.2704	$78.27	$78.25	$78.30
Purchase #5	$240.31	11.355%	$267.5972	$267.60	$267.60	$267.60
Purchase #6	$166.49	12.763%	$187.7391	$187.74	$187.75	$187.70
Purchase #7	$72.27	13.631%	$82.1211	$82.12	$82.10	$82.10
7 purchase totals =	$943.63		$1,030.7347	$1,030.73	$1,030.70	$1,030.70