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	$198.65	8.449%	$215.4339	$215.43	$215.45	$215.40
Purchase #2	$120.77	9.394%	$132.1151	$132.12	$132.10	$132.10
Purchase #3	$83.52	12.320%	$93.8097	$93.81	$93.80	$93.80
Purchase #4	$243.32	11.273%	$270.7495	$270.75	$270.75	$270.70
Purchase #5	$135.59	5.867%	$143.5451	$143.55	$143.55	$143.50
Purchase #6	$7.40	4.127%	$7.7054	$7.71	$7.70	$7.70
Purchase #7	$136.86	11.731%	$152.915	$152.92	$152.90	$152.90
7 purchase totals =	$926.11		$1,016.2737	$1,016.29	$1,016.25	$1,016.10