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	$192.69	3.833%	$200.0758	$200.08	$200.10	$200.10
Purchase #2	$154.58	12.832%	$174.4157	$174.42	$174.40	$174.40
Purchase #3	$162.41	6.460%	$172.9017	$172.90	$172.90	$172.90
Purchase #4	$172.80	6.383%	$183.8298	$183.83	$183.85	$183.80
Purchase #5	$166.53	11.339%	$185.4128	$185.41	$185.40	$185.40
Purchase #6	$18.33	12.814%	$20.6788	$20.68	$20.70	$20.70
Purchase #7	$246.58	3.569%	$255.3804	$255.38	$255.40	$255.40
7 purchase totals =	$1,113.92		$1,192.6950	$1,192.70	$1,192.75	$1,192.70