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	$93.63	11.654%	$104.5416	$104.54	$104.55	$104.50
Purchase #2	$191.73	9.587%	$210.1112	$210.11	$210.10	$210.10
Purchase #3	$112.71	11.419%	$125.5804	$125.58	$125.60	$125.60
Purchase #4	$100.52	10.692%	$111.2676	$111.27	$111.25	$111.30
Purchase #5	$109.40	8.286%	$118.4649	$118.46	$118.45	$118.50
Purchase #6	$176.89	5.515%	$186.6455	$186.65	$186.65	$186.60
Purchase #7	$20.31	10.260%	$22.3938	$22.39	$22.40	$22.40
7 purchase totals =	$805.19		$879.0050	$879.00	$879.00	$879.00