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	$210.60	4.769%	$220.6435	$220.64	$220.65	$220.60
Purchase #2	$70.32	13.273%	$79.6536	$79.65	$79.65	$79.70
Purchase #3	$9.93	9.172%	$10.8408	$10.84	$10.85	$10.80
Purchase #4	$41.69	4.239%	$43.4572	$43.46	$43.45	$43.50
Purchase #5	$245.71	12.825%	$277.2223	$277.22	$277.20	$277.20
Purchase #6	$236.69	11.842%	$264.7188	$264.72	$264.70	$264.70
Purchase #7	$201.44	6.734%	$215.005	$215.01	$215.00	$215.00
7 purchase totals =	$1,016.38		$1,111.5412	$1,111.54	$1,111.50	$1,111.50