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	$154.95	7.430%	$166.4628	$166.46	$166.45	$166.50
Purchase #2	$144.48	12.308%	$162.2626	$162.26	$162.25	$162.30
Purchase #3	$146.41	6.673%	$156.1799	$156.18	$156.20	$156.20
Purchase #4	$59.43	11.248%	$66.1147	$66.11	$66.10	$66.10
Purchase #5	$178.51	10.298%	$196.893	$196.89	$196.90	$196.90
Purchase #6	$22.68	8.331%	$24.5695	$24.57	$24.55	$24.60
Purchase #7	$150.88	8.793%	$164.1469	$164.15	$164.15	$164.10
7 purchase totals =	$857.34		$936.6294	$936.62	$936.60	$936.70