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	$55.45	6.868%	$59.2583	$59.26	$59.25	$59.30
Purchase #2	$168.40	3.353%	$174.0465	$174.05	$174.05	$174.00
Purchase #3	$249.27	8.828%	$271.2756	$271.28	$271.30	$271.30
Purchase #4	$26.85	9.452%	$29.3879	$29.39	$29.40	$29.40
Purchase #5	$155.90	6.182%	$165.5377	$165.54	$165.55	$165.50
Purchase #6	$99.68	5.807%	$105.4684	$105.47	$105.45	$105.50
Purchase #7	$229.91	3.511%	$237.9821	$237.98	$238.00	$238.00
7 purchase totals =	$985.46		$1,042.9565	$1,042.97	$1,043.00	$1,043.00