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	$89.33	6.505%	$95.1409	$95.14	$95.15	$95.10
Purchase #2	$112.61	3.370%	$116.405	$116.41	$116.40	$116.40
Purchase #3	$143.28	6.562%	$152.682	$152.68	$152.70	$152.70
Purchase #4	$129.80	10.526%	$143.4627	$143.46	$143.45	$143.50
Purchase #5	$167.52	11.353%	$186.5385	$186.54	$186.55	$186.50
Purchase #6	$116.84	5.298%	$123.0302	$123.03	$123.05	$123.00
Purchase #7	$52.40	6.729%	$55.926	$55.93	$55.95	$55.90
7 purchase totals =	$811.78		$873.1853	$873.19	$873.25	$873.10