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	$106.72	5.283%	$112.358	$112.36	$112.35	$112.40
Purchase #2	$64.46	6.179%	$68.443	$68.44	$68.45	$68.40
Purchase #3	$173.71	11.242%	$193.2385	$193.24	$193.25	$193.20
Purchase #4	$183.74	9.116%	$200.4897	$200.49	$200.50	$200.50
Purchase #5	$115.66	13.333%	$131.0809	$131.08	$131.10	$131.10
Purchase #6	$156.95	7.495%	$168.7134	$168.71	$168.70	$168.70
Purchase #7	$185.51	13.667%	$210.8637	$210.86	$210.85	$210.90
7 purchase totals =	$986.75		$1,085.1872	$1,085.18	$1,085.20	$1,085.20