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	$216.92	7.681%	$233.5816	$233.58	$233.60	$233.60
Purchase #2	$5.37	9.664%	$5.889	$5.89	$5.90	$5.90
Purchase #3	$152.52	8.512%	$165.5025	$165.50	$165.50	$165.50
Purchase #4	$101.75	10.534%	$112.4683	$112.47	$112.45	$112.50
Purchase #5	$131.84	8.775%	$143.409	$143.41	$143.40	$143.40
Purchase #6	$81.60	11.305%	$90.8249	$90.82	$90.80	$90.80
Purchase #7	$172.29	10.727%	$190.7715	$190.77	$190.75	$190.80
7 purchase totals =	$862.29		$942.4468	$942.44	$942.40	$942.50