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	$31.78	6.832%	$33.9512	$33.95	$33.95	$34.00
Purchase #2	$184.74	8.627%	$200.6775	$200.68	$200.70	$200.70
Purchase #3	$30.36	8.274%	$32.872	$32.87	$32.85	$32.90
Purchase #4	$165.35	8.191%	$178.8938	$178.89	$178.90	$178.90
Purchase #5	$205.69	13.300%	$233.0468	$233.05	$233.05	$233.00
Purchase #6	$242.43	11.241%	$269.6816	$269.68	$269.70	$269.70
Purchase #7	$179.41	9.657%	$196.7356	$196.74	$196.75	$196.70
7 purchase totals =	$1,039.76		$1,145.8585	$1,145.86	$1,145.90	$1,145.90