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	$148.60	7.674%	$160.0036	$160.00	$160.00	$160.00
Purchase #2	$123.30	7.298%	$132.2984	$132.30	$132.30	$132.30
Purchase #3	$99.75	4.271%	$104.0103	$104.01	$104.00	$104.00
Purchase #4	$145.74	9.171%	$159.1058	$159.11	$159.10	$159.10
Purchase #5	$156.59	4.784%	$164.0813	$164.08	$164.10	$164.10
Purchase #6	$66.41	13.654%	$75.4776	$75.48	$75.50	$75.50
Purchase #7	$61.48	7.178%	$65.893	$65.89	$65.90	$65.90
7 purchase totals =	$801.87		$860.8700	$860.87	$860.90	$860.90