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	$205.25	5.322%	$216.1734	$216.17	$216.15	$216.20
Purchase #2	$193.89	11.352%	$215.9004	$215.90	$215.90	$215.90
Purchase #3	$76.88	6.681%	$82.0164	$82.02	$82.00	$82.00
Purchase #4	$172.87	10.569%	$191.1406	$191.14	$191.15	$191.10
Purchase #5	$31.74	3.300%	$32.7874	$32.79	$32.80	$32.80
Purchase #6	$104.82	7.255%	$112.4247	$112.42	$112.40	$112.40
Purchase #7	$51.33	7.335%	$55.0951	$55.10	$55.10	$55.10
7 purchase totals =	$836.78		$905.5380	$905.54	$905.50	$905.50