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	$166.41	13.769%	$189.323	$189.32	$189.30	$189.30
Purchase #2	$35.87	7.304%	$38.4899	$38.49	$38.50	$38.50
Purchase #3	$187.46	12.546%	$210.9787	$210.98	$211.00	$211.00
Purchase #4	$186.29	12.112%	$208.8534	$208.85	$208.85	$208.90
Purchase #5	$51.47	11.833%	$57.5604	$57.56	$57.55	$57.60
Purchase #6	$170.29	9.747%	$186.8882	$186.89	$186.90	$186.90
Purchase #7	$55.53	12.173%	$62.2897	$62.29	$62.30	$62.30
7 purchase totals =	$853.32		$954.3833	$954.38	$954.40	$954.50