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	$148.31	9.412%	$162.2689	$162.27	$162.25	$162.30
Purchase #2	$17.39	8.628%	$18.8904	$18.89	$18.90	$18.90
Purchase #3	$177.50	10.751%	$196.583	$196.58	$196.60	$196.60
Purchase #4	$75.44	12.370%	$84.7719	$84.77	$84.75	$84.80
Purchase #5	$121.54	4.847%	$127.431	$127.43	$127.45	$127.40
Purchase #6	$58.60	8.213%	$63.4128	$63.41	$63.40	$63.40
Purchase #7	$182.37	3.607%	$188.9481	$188.95	$188.95	$188.90
7 purchase totals =	$781.15		$842.3061	$842.30	$842.30	$842.30