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	$227.45	11.269%	$253.0813	$253.08	$253.10	$253.10
Purchase #2	$13.52	5.861%	$14.3124	$14.31	$14.30	$14.30
Purchase #3	$218.73	11.251%	$243.3393	$243.34	$243.35	$243.30
Purchase #4	$56.62	5.808%	$59.9085	$59.91	$59.90	$59.90
Purchase #5	$57.78	10.563%	$63.8833	$63.88	$63.90	$63.90
Purchase #6	$103.49	3.763%	$107.3843	$107.38	$107.40	$107.40
Purchase #7	$47.91	3.520%	$49.5964	$49.60	$49.60	$49.60
7 purchase totals =	$725.50		$791.5055	$791.50	$791.55	$791.50