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	$87.78	9.520%	$96.1367	$96.14	$96.15	$96.10
Purchase #2	$213.90	11.392%	$238.2675	$238.27	$238.25	$238.30
Purchase #3	$227.27	7.807%	$245.013	$245.01	$245.00	$245.00
Purchase #4	$164.97	13.434%	$187.1321	$187.13	$187.15	$187.10
Purchase #5	$133.92	6.343%	$142.4145	$142.41	$142.40	$142.40
Purchase #6	$101.69	10.753%	$112.6247	$112.62	$112.60	$112.60
Purchase #7	$42.43	12.545%	$47.7528	$47.75	$47.75	$47.80
7 purchase totals =	$971.96		$1,069.3413	$1,069.33	$1,069.30	$1,069.30