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	$225.93	12.495%	$254.16	$254.16	$254.15	$254.20
Purchase #2	$73.60	11.838%	$82.3128	$82.31	$82.30	$82.30
Purchase #3	$221.84	11.858%	$248.1458	$248.15	$248.15	$248.10
Purchase #4	$195.82	9.578%	$214.5756	$214.58	$214.60	$214.60
Purchase #5	$82.30	7.124%	$88.1631	$88.16	$88.15	$88.20
Purchase #6	$127.37	10.784%	$141.1056	$141.11	$141.10	$141.10
Purchase #7	$102.67	11.430%	$114.4052	$114.41	$114.40	$114.40
7 purchase totals =	$1,029.53		$1,142.8681	$1,142.88	$1,142.85	$1,142.90