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	$52.50	6.125%	$55.7156	$55.72	$55.70	$55.70
Purchase #2	$212.83	6.731%	$227.1556	$227.16	$227.15	$227.20
Purchase #3	$207.34	13.764%	$235.8783	$235.88	$235.90	$235.90
Purchase #4	$225.36	13.384%	$255.5222	$255.52	$255.50	$255.50
Purchase #5	$185.87	13.154%	$210.3193	$210.32	$210.30	$210.30
Purchase #6	$45.37	7.796%	$48.907	$48.91	$48.90	$48.90
Purchase #7	$162.42	12.602%	$182.8882	$182.89	$182.90	$182.90
7 purchase totals =	$1,091.69		$1,216.3862	$1,216.40	$1,216.35	$1,216.40