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	$174.52	11.651%	$194.8533	$194.85	$194.85	$194.90
Purchase #2	$114.98	4.714%	$120.4002	$120.40	$120.40	$120.40
Purchase #3	$144.31	10.164%	$158.9777	$158.98	$159.00	$159.00
Purchase #4	$69.43	13.651%	$78.9079	$78.91	$78.90	$78.90
Purchase #5	$142.37	12.196%	$159.7334	$159.73	$159.75	$159.70
Purchase #6	$242.47	3.789%	$251.6572	$251.66	$251.65	$251.70
Purchase #7	$89.29	8.554%	$96.9279	$96.93	$96.95	$96.90
7 purchase totals =	$977.37		$1,061.4576	$1,061.46	$1,061.50	$1,061.50