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	$164.37	7.270%	$176.3197	$176.32	$176.30	$176.30
Purchase #2	$91.67	13.593%	$104.1307	$104.13	$104.15	$104.10
Purchase #3	$17.32	7.287%	$18.5821	$18.58	$18.60	$18.60
Purchase #4	$222.87	11.729%	$249.0104	$249.01	$249.00	$249.00
Purchase #5	$60.81	7.860%	$65.5897	$65.59	$65.60	$65.60
Purchase #6	$149.83	9.587%	$164.1942	$164.19	$164.20	$164.20
Purchase #7	$39.93	13.481%	$45.313	$45.31	$45.30	$45.30
7 purchase totals =	$746.80		$823.1398	$823.13	$823.15	$823.10