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	$224.85	8.747%	$244.5176	$244.52	$244.50	$244.50
Purchase #2	$165.98	9.428%	$181.6286	$181.63	$181.65	$181.60
Purchase #3	$119.37	5.131%	$125.4949	$125.49	$125.50	$125.50
Purchase #4	$140.98	7.492%	$151.5422	$151.54	$151.55	$151.50
Purchase #5	$202.48	5.404%	$213.422	$213.42	$213.40	$213.40
Purchase #6	$80.69	10.833%	$89.4311	$89.43	$89.45	$89.40
Purchase #7	$62.56	13.355%	$70.9149	$70.91	$70.90	$70.90
7 purchase totals =	$996.91		$1,076.9513	$1,076.94	$1,076.95	$1,076.80