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	$82.93	7.557%	$89.197	$89.20	$89.20	$89.20
Purchase #2	$95.79	6.293%	$101.8181	$101.82	$101.80	$101.80
Purchase #3	$28.52	12.245%	$32.0123	$32.01	$32.00	$32.00
Purchase #4	$187.49	11.423%	$208.907	$208.91	$208.90	$208.90
Purchase #5	$74.69	3.870%	$77.5805	$77.58	$77.60	$77.60
Purchase #6	$216.82	7.722%	$233.5628	$233.56	$233.55	$233.60
Purchase #7	$41.29	9.864%	$45.3628	$45.36	$45.35	$45.40
7 purchase totals =	$727.53		$788.4405	$788.44	$788.40	$788.50