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	$245.77	8.788%	$267.3683	$267.37	$267.35	$267.40
Purchase #2	$92.71	13.844%	$105.5448	$105.54	$105.55	$105.50
Purchase #3	$128.76	10.807%	$142.6751	$142.68	$142.70	$142.70
Purchase #4	$116.36	13.275%	$131.8068	$131.81	$131.80	$131.80
Purchase #5	$71.77	4.211%	$74.7922	$74.79	$74.80	$74.80
Purchase #6	$25.93	9.389%	$28.3646	$28.36	$28.35	$28.40
Purchase #7	$240.64	11.576%	$268.4965	$268.50	$268.50	$268.50
7 purchase totals =	$921.94		$1,019.0483	$1,019.05	$1,019.05	$1,019.10