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	$42.94	8.214%	$46.4671	$46.47	$46.45	$46.50
Purchase #2	$195.35	8.122%	$211.2163	$211.22	$211.20	$211.20
Purchase #3	$32.77	3.356%	$33.8698	$33.87	$33.85	$33.90
Purchase #4	$206.25	8.814%	$224.4289	$224.43	$224.45	$224.40
Purchase #5	$54.70	5.442%	$57.6768	$57.68	$57.70	$57.70
Purchase #6	$71.55	9.677%	$78.4739	$78.47	$78.45	$78.50
Purchase #7	$250.61	3.138%	$258.4741	$258.47	$258.45	$258.50
7 purchase totals =	$854.17		$910.6069	$910.61	$910.55	$910.70