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	$74.72	5.138%	$78.5591	$78.56	$78.55	$78.60
Purchase #2	$18.61	11.209%	$20.696	$20.70	$20.70	$20.70
Purchase #3	$244.97	9.429%	$268.0682	$268.07	$268.05	$268.10
Purchase #4	$138.98	6.237%	$147.6482	$147.65	$147.65	$147.60
Purchase #5	$121.34	4.591%	$126.9107	$126.91	$126.90	$126.90
Purchase #6	$224.39	9.371%	$245.4176	$245.42	$245.40	$245.40
Purchase #7	$116.54	11.208%	$129.6018	$129.60	$129.60	$129.60
7 purchase totals =	$939.55		$1,016.9016	$1,016.91	$1,016.85	$1,016.90