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	$228.37	10.179%	$251.6158	$251.62	$251.60	$251.60
Purchase #2	$85.98	7.320%	$92.2737	$92.27	$92.25	$92.30
Purchase #3	$226.40	4.447%	$236.468	$236.47	$236.45	$236.50
Purchase #4	$191.81	13.514%	$217.7312	$217.73	$217.75	$217.70
Purchase #5	$32.59	10.173%	$35.9054	$35.91	$35.90	$35.90
Purchase #6	$31.59	5.832%	$33.4323	$33.43	$33.45	$33.40
Purchase #7	$120.54	10.414%	$133.093	$133.09	$133.10	$133.10
7 purchase totals =	$917.28		$1,000.5194	$1,000.52	$1,000.50	$1,000.50