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	$104.31	6.655%	$111.2518	$111.25	$111.25	$111.30
Purchase #2	$170.99	7.525%	$183.857	$183.86	$183.85	$183.90
Purchase #3	$117.69	4.842%	$123.3885	$123.39	$123.40	$123.40
Purchase #4	$159.42	8.495%	$172.9627	$172.96	$172.95	$173.00
Purchase #5	$58.40	9.560%	$63.983	$63.98	$64.00	$64.00
Purchase #6	$18.91	13.791%	$21.5179	$21.52	$21.50	$21.50
Purchase #7	$14.73	9.311%	$16.1015	$16.10	$16.10	$16.10
7 purchase totals =	$644.45		$693.0624	$693.06	$693.05	$693.20