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	$57.35	4.164%	$59.7381	$59.74	$59.75	$59.70
Purchase #2	$43.25	4.234%	$45.0812	$45.08	$45.10	$45.10
Purchase #3	$23.58	5.336%	$24.8382	$24.84	$24.85	$24.80
Purchase #4	$248.46	5.466%	$262.0408	$262.04	$262.05	$262.00
Purchase #5	$63.62	12.588%	$71.6285	$71.63	$71.65	$71.60
Purchase #6	$166.70	6.735%	$177.9272	$177.93	$177.95	$177.90
Purchase #7	$169.90	12.360%	$190.8996	$190.90	$190.90	$190.90
7 purchase totals =	$772.86		$832.1536	$832.16	$832.25	$832.00