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	$87.85	5.614%	$92.7819	$92.78	$92.80	$92.80
Purchase #2	$38.86	3.637%	$40.2733	$40.27	$40.25	$40.30
Purchase #3	$244.25	4.589%	$255.4586	$255.46	$255.45	$255.50
Purchase #4	$82.91	5.532%	$87.4966	$87.50	$87.50	$87.50
Purchase #5	$67.44	8.507%	$73.1771	$73.18	$73.20	$73.20
Purchase #6	$62.93	5.352%	$66.298	$66.30	$66.30	$66.30
Purchase #7	$80.44	12.294%	$90.3293	$90.33	$90.35	$90.30
7 purchase totals =	$664.68		$705.8148	$705.82	$705.85	$705.90