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	$10.61	7.713%	$11.4283	$11.43	$11.45	$11.40
Purchase #2	$215.67	4.595%	$225.58	$225.58	$225.60	$225.60
Purchase #3	$79.94	13.260%	$90.54	$90.54	$90.55	$90.50
Purchase #4	$108.99	8.269%	$118.0024	$118.00	$118.00	$118.00
Purchase #5	$131.53	12.415%	$147.8594	$147.86	$147.85	$147.90
Purchase #6	$102.66	8.526%	$111.4128	$111.41	$111.40	$111.40
Purchase #7	$112.33	7.376%	$120.6155	$120.62	$120.60	$120.60
7 purchase totals =	$761.73		$825.4384	$825.44	$825.45	$825.40