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	$220.83	3.738%	$229.0846	$229.08	$229.10	$229.10
Purchase #2	$127.49	9.842%	$140.0376	$140.04	$140.05	$140.00
Purchase #3	$78.56	6.152%	$83.393	$83.39	$83.40	$83.40
Purchase #4	$170.88	10.203%	$188.3149	$188.31	$188.30	$188.30
Purchase #5	$72.89	5.544%	$76.931	$76.93	$76.95	$76.90
Purchase #6	$229.83	5.641%	$242.7947	$242.79	$242.80	$242.80
Purchase #7	$117.66	12.398%	$132.2475	$132.25	$132.25	$132.20
7 purchase totals =	$1,018.14		$1,092.8033	$1,092.79	$1,092.85	$1,092.70