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	$180.37	3.654%	$186.9607	$186.96	$186.95	$187.00
Purchase #2	$218.41	11.635%	$243.822	$243.82	$243.80	$243.80
Purchase #3	$200.56	8.631%	$217.8703	$217.87	$217.85	$217.90
Purchase #4	$194.28	3.215%	$200.5261	$200.53	$200.55	$200.50
Purchase #5	$163.32	13.379%	$185.1706	$185.17	$185.15	$185.20
Purchase #6	$18.84	7.464%	$20.2462	$20.25	$20.25	$20.20
Purchase #7	$82.43	13.825%	$93.8259	$93.83	$93.85	$93.80
7 purchase totals =	$1,058.21		$1,148.4218	$1,148.43	$1,148.40	$1,148.40