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	$65.56	3.581%	$67.9077	$67.91	$67.90	$67.90
Purchase #2	$148.42	9.682%	$162.79	$162.79	$162.80	$162.80
Purchase #3	$136.42	4.712%	$142.8481	$142.85	$142.85	$142.80
Purchase #4	$241.73	11.609%	$269.7924	$269.79	$269.80	$269.80
Purchase #5	$148.25	7.363%	$159.1656	$159.17	$159.15	$159.20
Purchase #6	$103.36	6.771%	$110.3585	$110.36	$110.35	$110.40
Purchase #7	$239.86	11.136%	$266.5708	$266.57	$266.55	$266.60
7 purchase totals =	$1,083.60		$1,179.4331	$1,179.44	$1,179.40	$1,179.50