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	$141.75	8.441%	$153.7151	$153.72	$153.70	$153.70
Purchase #2	$100.37	4.117%	$104.5022	$104.50	$104.50	$104.50
Purchase #3	$154.77	6.557%	$164.9183	$164.92	$164.90	$164.90
Purchase #4	$19.37	4.426%	$20.2273	$20.23	$20.25	$20.20
Purchase #5	$121.98	8.279%	$132.0787	$132.08	$132.10	$132.10
Purchase #6	$150.33	3.352%	$155.3691	$155.37	$155.35	$155.40
Purchase #7	$82.74	3.102%	$85.3066	$85.31	$85.30	$85.30
7 purchase totals =	$771.31		$816.1173	$816.13	$816.10	$816.10