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	$242.36	11.144%	$269.3686	$269.37	$269.35	$269.40
Purchase #2	$102.72	8.157%	$111.0989	$111.10	$111.10	$111.10
Purchase #3	$139.28	7.695%	$149.9976	$150.00	$150.00	$150.00
Purchase #4	$106.83	5.725%	$112.946	$112.95	$112.95	$112.90
Purchase #5	$95.43	7.597%	$102.6798	$102.68	$102.70	$102.70
Purchase #6	$235.98	13.810%	$268.5688	$268.57	$268.55	$268.60
Purchase #7	$166.73	3.218%	$172.0954	$172.10	$172.10	$172.10
7 purchase totals =	$1,089.33		$1,186.7551	$1,186.77	$1,186.75	$1,186.80