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	$224.51	10.694%	$248.5191	$248.52	$248.50	$248.50
Purchase #2	$125.57	12.614%	$141.4094	$141.41	$141.40	$141.40
Purchase #3	$215.73	8.383%	$233.8146	$233.81	$233.80	$233.80
Purchase #4	$81.41	6.368%	$86.5942	$86.59	$86.60	$86.60
Purchase #5	$215.50	11.426%	$240.123	$240.12	$240.10	$240.10
Purchase #6	$188.83	4.798%	$197.8901	$197.89	$197.90	$197.90
Purchase #7	$189.48	10.434%	$209.2503	$209.25	$209.25	$209.30
7 purchase totals =	$1,241.03		$1,357.6007	$1,357.59	$1,357.55	$1,357.60