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	$246.87	4.166%	$257.1546	$257.15	$257.15	$257.20
Purchase #2	$100.62	7.610%	$108.2772	$108.28	$108.30	$108.30
Purchase #3	$152.50	12.457%	$171.4969	$171.50	$171.50	$171.50
Purchase #4	$166.61	5.858%	$176.37	$176.37	$176.35	$176.40
Purchase #5	$32.86	4.476%	$34.3308	$34.33	$34.35	$34.30
Purchase #6	$49.51	12.147%	$55.524	$55.52	$55.50	$55.50
Purchase #7	$233.27	4.830%	$244.5369	$244.54	$244.55	$244.50
7 purchase totals =	$982.24		$1,047.6904	$1,047.69	$1,047.70	$1,047.70