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	$179.82	11.681%	$200.8248	$200.82	$200.80	$200.80
Purchase #2	$207.75	7.389%	$223.1006	$223.10	$223.10	$223.10
Purchase #3	$8.34	12.852%	$9.4119	$9.41	$9.40	$9.40
Purchase #4	$236.58	10.784%	$262.0928	$262.09	$262.10	$262.10
Purchase #5	$70.71	11.142%	$78.5885	$78.59	$78.60	$78.60
Purchase #6	$130.46	6.480%	$138.9138	$138.91	$138.90	$138.90
Purchase #7	$90.63	12.483%	$101.9433	$101.94	$101.95	$101.90
7 purchase totals =	$924.29		$1,014.8757	$1,014.86	$1,014.85	$1,014.80