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	$174.92	12.550%	$196.8725	$196.87	$196.85	$196.90
Purchase #2	$39.52	3.270%	$40.8123	$40.81	$40.80	$40.80
Purchase #3	$242.31	7.272%	$259.9308	$259.93	$259.95	$259.90
Purchase #4	$228.59	8.851%	$248.8225	$248.82	$248.80	$248.80
Purchase #5	$142.54	4.866%	$149.476	$149.48	$149.50	$149.50
Purchase #6	$236.36	6.412%	$251.5154	$251.52	$251.50	$251.50
Purchase #7	$31.82	10.704%	$35.226	$35.23	$35.25	$35.20
7 purchase totals =	$1,096.06		$1,182.6555	$1,182.66	$1,182.65	$1,182.60