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	$168.54	8.230%	$182.4108	$182.41	$182.40	$182.40
Purchase #2	$92.52	6.762%	$98.7762	$98.78	$98.80	$98.80
Purchase #3	$204.70	7.373%	$219.7925	$219.79	$219.80	$219.80
Purchase #4	$54.37	9.319%	$59.4367	$59.44	$59.45	$59.40
Purchase #5	$39.44	11.694%	$44.0521	$44.05	$44.05	$44.10
Purchase #6	$101.83	9.262%	$111.2615	$111.26	$111.25	$111.30
Purchase #7	$78.37	8.873%	$85.3238	$85.32	$85.30	$85.30
7 purchase totals =	$739.77		$801.0536	$801.05	$801.05	$801.10