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	$200.25	11.818%	$223.9155	$223.92	$223.90	$223.90
Purchase #2	$177.46	12.107%	$198.9451	$198.95	$198.95	$198.90
Purchase #3	$57.98	3.233%	$59.8545	$59.85	$59.85	$59.90
Purchase #4	$213.88	12.809%	$241.2759	$241.28	$241.30	$241.30
Purchase #5	$29.43	3.745%	$30.5322	$30.53	$30.55	$30.50
Purchase #6	$159.97	7.186%	$171.4654	$171.47	$171.45	$171.50
Purchase #7	$135.98	4.492%	$142.0882	$142.09	$142.10	$142.10
7 purchase totals =	$974.95		$1,068.0768	$1,068.09	$1,068.10	$1,068.10