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	$123.69	7.432%	$132.8826	$132.88	$132.90	$132.90
Purchase #2	$28.88	3.862%	$29.9953	$30.00	$30.00	$30.00
Purchase #3	$241.55	13.403%	$273.9249	$273.92	$273.90	$273.90
Purchase #4	$203.65	9.561%	$223.121	$223.12	$223.10	$223.10
Purchase #5	$49.38	6.792%	$52.7339	$52.73	$52.75	$52.70
Purchase #6	$82.83	8.407%	$89.7935	$89.79	$89.80	$89.80
Purchase #7	$241.54	4.686%	$252.8586	$252.86	$252.85	$252.90
7 purchase totals =	$971.52		$1,055.3098	$1,055.30	$1,055.30	$1,055.30