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	$222.38	9.769%	$244.1043	$244.10	$244.10	$244.10
Purchase #2	$214.97	3.856%	$223.2592	$223.26	$223.25	$223.30
Purchase #3	$178.51	6.649%	$190.3791	$190.38	$190.40	$190.40
Purchase #4	$164.91	5.598%	$174.1417	$174.14	$174.15	$174.10
Purchase #5	$18.63	5.625%	$19.6779	$19.68	$19.70	$19.70
Purchase #6	$71.52	9.726%	$78.476	$78.48	$78.50	$78.50
Purchase #7	$218.56	5.825%	$231.2911	$231.29	$231.30	$231.30
7 purchase totals =	$1,089.48		$1,161.3293	$1,161.33	$1,161.40	$1,161.40