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	$122.93	3.341%	$127.0371	$127.04	$127.05	$127.00
Purchase #2	$187.38	6.823%	$200.1649	$200.16	$200.15	$200.20
Purchase #3	$176.27	13.399%	$199.8884	$199.89	$199.90	$199.90
Purchase #4	$164.33	4.406%	$171.5704	$171.57	$171.55	$171.60
Purchase #5	$121.69	5.250%	$128.0787	$128.08	$128.10	$128.10
Purchase #6	$78.66	11.585%	$87.7728	$87.77	$87.75	$87.80
Purchase #7	$120.25	10.487%	$132.8606	$132.86	$132.85	$132.90
7 purchase totals =	$971.51		$1,047.3729	$1,047.37	$1,047.35	$1,047.50