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	$151.37	7.586%	$162.8529	$162.85	$162.85	$162.90
Purchase #2	$64.41	5.840%	$68.1715	$68.17	$68.15	$68.20
Purchase #3	$121.39	8.375%	$131.5564	$131.56	$131.55	$131.60
Purchase #4	$239.44	7.491%	$257.3765	$257.38	$257.40	$257.40
Purchase #5	$215.90	8.271%	$233.7571	$233.76	$233.75	$233.80
Purchase #6	$100.43	8.783%	$109.2508	$109.25	$109.25	$109.30
Purchase #7	$38.92	11.452%	$43.3771	$43.38	$43.40	$43.40
7 purchase totals =	$931.86		$1,006.3423	$1,006.35	$1,006.35	$1,006.60