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	$201.77	7.286%	$216.471	$216.47	$216.45	$216.50
Purchase #2	$136.86	3.626%	$141.8225	$141.82	$141.80	$141.80
Purchase #3	$176.95	7.326%	$189.9134	$189.91	$189.90	$189.90
Purchase #4	$225.89	11.601%	$252.0955	$252.10	$252.10	$252.10
Purchase #5	$212.46	5.225%	$223.561	$223.56	$223.55	$223.60
Purchase #6	$41.57	10.258%	$45.8343	$45.83	$45.85	$45.80
Purchase #7	$81.42	6.124%	$86.4062	$86.41	$86.40	$86.40
7 purchase totals =	$1,076.92		$1,156.1039	$1,156.10	$1,156.05	$1,156.10