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	$83.38	3.329%	$86.1557	$86.16	$86.15	$86.20
Purchase #2	$149.44	7.290%	$160.3342	$160.33	$160.35	$160.30
Purchase #3	$78.78	4.381%	$82.2314	$82.23	$82.25	$82.20
Purchase #4	$135.89	8.606%	$147.5847	$147.58	$147.60	$147.60
Purchase #5	$71.77	9.120%	$78.3154	$78.32	$78.30	$78.30
Purchase #6	$186.39	3.582%	$193.0665	$193.07	$193.05	$193.10
Purchase #7	$23.49	8.729%	$25.5404	$25.54	$25.55	$25.50
7 purchase totals =	$729.14		$773.2283	$773.23	$773.25	$773.20