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	$79.29	10.776%	$87.8343	$87.83	$87.85	$87.80
Purchase #2	$199.28	3.656%	$206.5657	$206.57	$206.55	$206.60
Purchase #3	$79.75	8.425%	$86.4689	$86.47	$86.45	$86.50
Purchase #4	$186.49	4.165%	$194.2573	$194.26	$194.25	$194.30
Purchase #5	$247.29	5.612%	$261.1679	$261.17	$261.15	$261.20
Purchase #6	$89.97	10.191%	$99.1388	$99.14	$99.15	$99.10
Purchase #7	$85.39	6.379%	$90.837	$90.84	$90.85	$90.80
7 purchase totals =	$967.46		$1,026.2699	$1,026.28	$1,026.25	$1,026.30