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	$185.59	12.102%	$208.0501	$208.05	$208.05	$208.10
Purchase #2	$238.45	6.628%	$254.2545	$254.25	$254.25	$254.30
Purchase #3	$71.98	4.575%	$75.2731	$75.27	$75.25	$75.30
Purchase #4	$157.57	3.394%	$162.9179	$162.92	$162.90	$162.90
Purchase #5	$220.69	11.268%	$245.5573	$245.56	$245.55	$245.60
Purchase #6	$61.54	9.272%	$67.246	$67.25	$67.25	$67.20
Purchase #7	$64.98	11.242%	$72.2851	$72.29	$72.30	$72.30
7 purchase totals =	$1,000.80		$1,085.5840	$1,085.59	$1,085.55	$1,085.70