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	$154.56	12.485%	$173.8568	$173.86	$173.85	$173.90
Purchase #2	$194.37	5.742%	$205.5307	$205.53	$205.55	$205.50
Purchase #3	$244.46	9.849%	$268.5369	$268.54	$268.55	$268.50
Purchase #4	$100.55	10.768%	$111.3772	$111.38	$111.40	$111.40
Purchase #5	$138.58	7.256%	$148.6354	$148.64	$148.65	$148.60
Purchase #6	$199.66	5.742%	$211.1245	$211.12	$211.10	$211.10
Purchase #7	$33.53	12.814%	$37.8265	$37.83	$37.85	$37.80
7 purchase totals =	$1,065.71		$1,156.8880	$1,156.90	$1,156.95	$1,156.80