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	$85.26	8.541%	$92.5421	$92.54	$92.55	$92.50
Purchase #2	$170.68	10.543%	$188.6748	$188.67	$188.65	$188.70
Purchase #3	$239.27	6.381%	$254.5378	$254.54	$254.55	$254.50
Purchase #4	$247.96	10.536%	$274.0851	$274.09	$274.10	$274.10
Purchase #5	$94.46	5.826%	$99.9632	$99.96	$99.95	$100.00
Purchase #6	$21.44	11.850%	$23.9806	$23.98	$24.00	$24.00
Purchase #7	$61.65	9.801%	$67.6923	$67.69	$67.70	$67.70
7 purchase totals =	$920.72		$1,001.4759	$1,001.47	$1,001.50	$1,001.50