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	$185.57	5.808%	$196.3479	$196.35	$196.35	$196.30
Purchase #2	$136.92	7.381%	$147.0261	$147.03	$147.05	$147.00
Purchase #3	$85.88	11.300%	$95.5844	$95.58	$95.60	$95.60
Purchase #4	$35.59	10.651%	$39.3807	$39.38	$39.40	$39.40
Purchase #5	$100.91	11.321%	$112.334	$112.33	$112.35	$112.30
Purchase #6	$128.54	12.461%	$144.5574	$144.56	$144.55	$144.60
Purchase #7	$76.35	12.623%	$85.9877	$85.99	$86.00	$86.00
7 purchase totals =	$749.76		$821.2182	$821.22	$821.30	$821.20