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	$181.89	10.355%	$200.7247	$200.72	$200.70	$200.70
Purchase #2	$77.68	6.873%	$83.0189	$83.02	$83.00	$83.00
Purchase #3	$187.55	8.380%	$203.2667	$203.27	$203.25	$203.30
Purchase #4	$55.36	10.504%	$61.175	$61.18	$61.20	$61.20
Purchase #5	$145.96	7.334%	$156.6647	$156.66	$156.65	$156.70
Purchase #6	$127.28	9.569%	$139.4594	$139.46	$139.45	$139.50
Purchase #7	$90.25	8.171%	$97.6243	$97.62	$97.60	$97.60
7 purchase totals =	$865.97		$941.9337	$941.93	$941.85	$942.00