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	$54.89	5.207%	$57.7481	$57.75	$57.75	$57.70
Purchase #2	$95.64	11.248%	$106.3976	$106.40	$106.40	$106.40
Purchase #3	$80.60	10.755%	$89.2685	$89.27	$89.25	$89.30
Purchase #4	$217.56	4.492%	$227.3328	$227.33	$227.35	$227.30
Purchase #5	$133.28	11.650%	$148.8071	$148.81	$148.80	$148.80
Purchase #6	$235.52	5.253%	$247.8919	$247.89	$247.90	$247.90
Purchase #7	$149.67	9.783%	$164.3122	$164.31	$164.30	$164.30
7 purchase totals =	$967.16		$1,041.7582	$1,041.76	$1,041.75	$1,041.70