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	$104.38	9.129%	$113.9089	$113.91	$113.90	$113.90
Purchase #2	$151.50	7.474%	$162.8231	$162.82	$162.80	$162.80
Purchase #3	$156.99	6.522%	$167.2289	$167.23	$167.25	$167.20
Purchase #4	$171.73	11.106%	$190.8023	$190.80	$190.80	$190.80
Purchase #5	$146.34	13.243%	$165.7198	$165.72	$165.70	$165.70
Purchase #6	$104.42	7.520%	$112.2724	$112.27	$112.25	$112.30
Purchase #7	$134.70	12.594%	$151.6641	$151.66	$151.65	$151.70
7 purchase totals =	$970.06		$1,064.4195	$1,064.41	$1,064.35	$1,064.40