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	$153.81	13.570%	$174.682	$174.68	$174.70	$174.70
Purchase #2	$98.27	10.356%	$108.4468	$108.45	$108.45	$108.40
Purchase #3	$250.62	5.631%	$264.7324	$264.73	$264.75	$264.70
Purchase #4	$105.75	7.250%	$113.4169	$113.42	$113.40	$113.40
Purchase #5	$70.49	11.404%	$78.5287	$78.53	$78.55	$78.50
Purchase #6	$245.77	8.147%	$265.7929	$265.79	$265.80	$265.80
Purchase #7	$45.37	9.722%	$49.7809	$49.78	$49.80	$49.80
7 purchase totals =	$970.08		$1,055.3806	$1,055.38	$1,055.45	$1,055.30