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	$244.39	5.355%	$257.4771	$257.48	$257.50	$257.50
Purchase #2	$36.88	9.681%	$40.4504	$40.45	$40.45	$40.50
Purchase #3	$81.91	13.765%	$93.1849	$93.18	$93.20	$93.20
Purchase #4	$105.55	10.740%	$116.8861	$116.89	$116.90	$116.90
Purchase #5	$190.27	3.498%	$196.9256	$196.93	$196.95	$196.90
Purchase #6	$58.56	7.321%	$62.8472	$62.85	$62.85	$62.80
Purchase #7	$89.44	13.425%	$101.4473	$101.45	$101.45	$101.40
7 purchase totals =	$807.00		$869.2186	$869.23	$869.30	$869.20