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	$169.91	3.210%	$175.3641	$175.36	$175.35	$175.40
Purchase #2	$99.31	9.742%	$108.9848	$108.98	$109.00	$109.00
Purchase #3	$65.63	8.578%	$71.2597	$71.26	$71.25	$71.30
Purchase #4	$39.65	7.127%	$42.4759	$42.48	$42.50	$42.50
Purchase #5	$123.76	10.743%	$137.0555	$137.06	$137.05	$137.10
Purchase #6	$228.73	11.636%	$255.345	$255.35	$255.35	$255.30
Purchase #7	$61.97	10.617%	$68.5494	$68.55	$68.55	$68.50
7 purchase totals =	$788.96		$859.0344	$859.04	$859.05	$859.10