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	$217.54	7.242%	$233.2942	$233.29	$233.30	$233.30
Purchase #2	$67.52	4.496%	$70.5557	$70.56	$70.55	$70.60
Purchase #3	$59.85	3.762%	$62.1016	$62.10	$62.10	$62.10
Purchase #4	$187.49	5.826%	$198.4132	$198.41	$198.40	$198.40
Purchase #5	$56.41	3.338%	$58.293	$58.29	$58.30	$58.30
Purchase #6	$121.98	4.155%	$127.0483	$127.05	$127.05	$127.00
Purchase #7	$73.39	12.800%	$82.7839	$82.78	$82.80	$82.80
7 purchase totals =	$784.18		$832.4899	$832.48	$832.50	$832.50