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	$95.33	11.120%	$105.9307	$105.93	$105.95	$105.90
Purchase #2	$235.91	9.836%	$259.1141	$259.11	$259.10	$259.10
Purchase #3	$211.83	4.605%	$221.5848	$221.58	$221.60	$221.60
Purchase #4	$178.91	3.651%	$185.442	$185.44	$185.45	$185.40
Purchase #5	$172.34	11.680%	$192.4693	$192.47	$192.45	$192.50
Purchase #6	$52.36	12.711%	$59.0155	$59.02	$59.00	$59.00
Purchase #7	$50.40	4.653%	$52.7451	$52.75	$52.75	$52.70
7 purchase totals =	$997.08		$1,076.3015	$1,076.30	$1,076.30	$1,076.20