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	$154.80	9.572%	$169.6175	$169.62	$169.60	$169.60
Purchase #2	$77.29	7.218%	$82.8688	$82.87	$82.85	$82.90
Purchase #3	$183.98	6.141%	$195.2782	$195.28	$195.30	$195.30
Purchase #4	$150.55	13.459%	$170.8125	$170.81	$170.80	$170.80
Purchase #5	$120.38	6.821%	$128.5911	$128.59	$128.60	$128.60
Purchase #6	$82.28	11.547%	$91.7809	$91.78	$91.80	$91.80
Purchase #7	$160.66	5.421%	$169.3694	$169.37	$169.35	$169.40
7 purchase totals =	$929.94		$1,008.3184	$1,008.32	$1,008.30	$1,008.40