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	$211.84	7.340%	$227.3891	$227.39	$227.40	$227.40
Purchase #2	$126.54	13.333%	$143.4116	$143.41	$143.40	$143.40
Purchase #3	$125.38	5.167%	$131.8584	$131.86	$131.85	$131.90
Purchase #4	$8.39	6.147%	$8.9057	$8.91	$8.90	$8.90
Purchase #5	$174.67	5.549%	$184.3624	$184.36	$184.35	$184.40
Purchase #6	$117.83	8.422%	$127.7536	$127.75	$127.75	$127.80
Purchase #7	$238.48	12.496%	$268.2805	$268.28	$268.30	$268.30
7 purchase totals =	$1,003.13		$1,091.9613	$1,091.96	$1,091.95	$1,092.10