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	$112.87	3.545%	$116.8712	$116.87	$116.85	$116.90
Purchase #2	$65.88	9.404%	$72.0754	$72.08	$72.10	$72.10
Purchase #3	$54.91	3.834%	$57.0152	$57.02	$57.00	$57.00
Purchase #4	$103.77	8.155%	$112.2324	$112.23	$112.25	$112.20
Purchase #5	$175.62	12.133%	$196.928	$196.93	$196.95	$196.90
Purchase #6	$74.59	13.861%	$84.9289	$84.93	$84.95	$84.90
Purchase #7	$228.85	4.343%	$238.789	$238.79	$238.80	$238.80
7 purchase totals =	$816.49		$878.8401	$878.85	$878.90	$878.80