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	$124.81	5.187%	$131.2839	$131.28	$131.30	$131.30
Purchase #2	$247.51	4.293%	$258.1356	$258.14	$258.15	$258.10
Purchase #3	$69.57	3.618%	$72.087	$72.09	$72.10	$72.10
Purchase #4	$51.70	5.191%	$54.3837	$54.38	$54.40	$54.40
Purchase #5	$104.97	8.250%	$113.63	$113.63	$113.65	$113.60
Purchase #6	$146.59	4.817%	$153.6512	$153.65	$153.65	$153.70
Purchase #7	$173.37	9.223%	$189.3599	$189.36	$189.35	$189.40
7 purchase totals =	$918.52		$972.5313	$972.53	$972.60	$972.60