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	$212.52	13.315%	$240.817	$240.82	$240.80	$240.80
Purchase #2	$39.33	11.336%	$43.7884	$43.79	$43.80	$43.80
Purchase #3	$35.77	4.528%	$37.3897	$37.39	$37.40	$37.40
Purchase #4	$242.98	12.343%	$272.971	$272.97	$272.95	$273.00
Purchase #5	$238.88	13.163%	$270.3238	$270.32	$270.30	$270.30
Purchase #6	$235.79	9.840%	$258.9917	$258.99	$259.00	$259.00
Purchase #7	$93.69	12.620%	$105.5137	$105.51	$105.50	$105.50
7 purchase totals =	$1,098.96		$1,229.7953	$1,229.79	$1,229.75	$1,229.80