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	$133.52	10.281%	$147.2472	$147.25	$147.25	$147.20
Purchase #2	$170.94	4.608%	$178.8169	$178.82	$178.80	$178.80
Purchase #3	$91.40	4.720%	$95.7141	$95.71	$95.70	$95.70
Purchase #4	$36.86	5.420%	$38.8578	$38.86	$38.85	$38.90
Purchase #5	$243.93	12.774%	$275.0896	$275.09	$275.10	$275.10
Purchase #6	$72.81	7.362%	$78.1703	$78.17	$78.15	$78.20
Purchase #7	$86.87	10.548%	$96.033	$96.03	$96.05	$96.00
7 purchase totals =	$836.33		$909.9289	$909.93	$909.90	$909.90