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	$164.30	13.454%	$186.4049	$186.40	$186.40	$186.40
Purchase #2	$232.54	11.335%	$258.8984	$258.90	$258.90	$258.90
Purchase #3	$112.90	6.137%	$119.8287	$119.83	$119.85	$119.80
Purchase #4	$215.56	10.805%	$238.8513	$238.85	$238.85	$238.90
Purchase #5	$76.36	13.584%	$86.7327	$86.73	$86.75	$86.70
Purchase #6	$145.94	12.506%	$164.1913	$164.19	$164.20	$164.20
Purchase #7	$160.96	3.321%	$166.3055	$166.31	$166.30	$166.30
7 purchase totals =	$1,108.56		$1,221.2128	$1,221.21	$1,221.25	$1,221.20