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	$50.68	10.196%	$55.8473	$55.85	$55.85	$55.80
Purchase #2	$74.36	5.339%	$78.3301	$78.33	$78.35	$78.30
Purchase #3	$54.81	8.179%	$59.2929	$59.29	$59.30	$59.30
Purchase #4	$165.91	10.464%	$183.2708	$183.27	$183.25	$183.30
Purchase #5	$41.83	12.604%	$47.1023	$47.10	$47.10	$47.10
Purchase #6	$17.31	5.647%	$18.2875	$18.29	$18.30	$18.30
Purchase #7	$188.71	13.824%	$214.7973	$214.80	$214.80	$214.80
7 purchase totals =	$593.61		$656.9282	$656.93	$656.95	$656.90