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	$185.97	9.737%	$204.0779	$204.08	$204.10	$204.10
Purchase #2	$9.87	6.690%	$10.5303	$10.53	$10.55	$10.50
Purchase #3	$109.95	4.112%	$114.4711	$114.47	$114.45	$114.50
Purchase #4	$123.42	3.292%	$127.483	$127.48	$127.50	$127.50
Purchase #5	$134.85	9.182%	$147.2319	$147.23	$147.25	$147.20
Purchase #6	$226.39	7.162%	$242.6041	$242.60	$242.60	$242.60
Purchase #7	$161.88	3.455%	$167.473	$167.47	$167.45	$167.50
7 purchase totals =	$952.33		$1,013.8713	$1,013.86	$1,013.90	$1,013.90