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	$94.34	10.834%	$104.5608	$104.56	$104.55	$104.60
Purchase #2	$237.28	7.622%	$255.3655	$255.37	$255.35	$255.40
Purchase #3	$128.63	3.104%	$132.6227	$132.62	$132.60	$132.60
Purchase #4	$179.36	9.432%	$196.2772	$196.28	$196.30	$196.30
Purchase #5	$115.91	13.611%	$131.6865	$131.69	$131.70	$131.70
Purchase #6	$71.48	7.219%	$76.6401	$76.64	$76.65	$76.60
Purchase #7	$218.38	7.284%	$234.2868	$234.29	$234.30	$234.30
7 purchase totals =	$1,045.38		$1,131.4396	$1,131.45	$1,131.45	$1,131.50