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	$179.71	4.332%	$187.495	$187.50	$187.50	$187.50
Purchase #2	$86.32	5.346%	$90.9347	$90.93	$90.95	$90.90
Purchase #3	$149.90	9.481%	$164.112	$164.11	$164.10	$164.10
Purchase #4	$139.35	12.629%	$156.9485	$156.95	$156.95	$156.90
Purchase #5	$43.49	4.279%	$45.3509	$45.35	$45.35	$45.40
Purchase #6	$209.90	10.117%	$231.1356	$231.14	$231.15	$231.10
Purchase #7	$54.56	11.838%	$61.0188	$61.02	$61.00	$61.00
7 purchase totals =	$863.23		$936.9955	$937.00	$937.00	$936.90