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	$235.54	12.158%	$264.177	$264.18	$264.20	$264.20
Purchase #2	$169.78	10.779%	$188.0806	$188.08	$188.10	$188.10
Purchase #3	$118.27	7.672%	$127.3437	$127.34	$127.35	$127.30
Purchase #4	$71.90	7.238%	$77.1041	$77.10	$77.10	$77.10
Purchase #5	$81.65	4.814%	$85.5806	$85.58	$85.60	$85.60
Purchase #6	$170.68	11.618%	$190.5096	$190.51	$190.50	$190.50
Purchase #7	$183.52	12.322%	$206.1333	$206.13	$206.15	$206.10
7 purchase totals =	$1,031.34		$1,138.9289	$1,138.92	$1,139.00	$1,138.90