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	$201.86	4.372%	$210.6853	$210.69	$210.70	$210.70
Purchase #2	$222.43	6.185%	$236.1873	$236.19	$236.20	$236.20
Purchase #3	$90.42	11.326%	$100.661	$100.66	$100.65	$100.70
Purchase #4	$83.36	8.521%	$90.4631	$90.46	$90.45	$90.50
Purchase #5	$147.97	9.563%	$162.1204	$162.12	$162.10	$162.10
Purchase #6	$58.49	5.809%	$61.8877	$61.89	$61.90	$61.90
Purchase #7	$47.97	5.807%	$50.7556	$50.76	$50.75	$50.80
7 purchase totals =	$852.50		$912.7604	$912.77	$912.75	$912.90