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	$241.78	9.866%	$265.634	$265.63	$265.65	$265.60
Purchase #2	$168.27	8.600%	$182.7412	$182.74	$182.75	$182.70
Purchase #3	$193.42	8.270%	$209.4158	$209.42	$209.40	$209.40
Purchase #4	$98.58	13.551%	$111.9386	$111.94	$111.95	$111.90
Purchase #5	$199.47	9.802%	$219.022	$219.02	$219.00	$219.00
Purchase #6	$87.50	3.263%	$90.3551	$90.36	$90.35	$90.40
Purchase #7	$95.89	10.619%	$106.0726	$106.07	$106.05	$106.10
7 purchase totals =	$1,084.91		$1,185.1793	$1,185.18	$1,185.15	$1,185.10