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	$99.27	10.157%	$109.3529	$109.35	$109.35	$109.40
Purchase #2	$174.65	11.410%	$194.5776	$194.58	$194.60	$194.60
Purchase #3	$167.75	13.365%	$190.1698	$190.17	$190.15	$190.20
Purchase #4	$92.78	11.303%	$103.2669	$103.27	$103.25	$103.30
Purchase #5	$172.56	13.814%	$196.3974	$196.40	$196.40	$196.40
Purchase #6	$13.70	10.851%	$15.1866	$15.19	$15.20	$15.20
Purchase #7	$46.73	4.423%	$48.7969	$48.80	$48.80	$48.80
7 purchase totals =	$767.44		$857.7481	$857.76	$857.75	$857.90