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	$23.85	8.529%	$25.8842	$25.88	$25.90	$25.90
Purchase #2	$232.70	13.670%	$264.5101	$264.51	$264.50	$264.50
Purchase #3	$70.40	11.354%	$78.3932	$78.39	$78.40	$78.40
Purchase #4	$238.41	13.676%	$271.015	$271.02	$271.00	$271.00
Purchase #5	$95.37	8.210%	$103.1999	$103.20	$103.20	$103.20
Purchase #6	$74.25	7.202%	$79.5975	$79.60	$79.60	$79.60
Purchase #7	$221.51	3.380%	$228.997	$229.00	$229.00	$229.00
7 purchase totals =	$956.49		$1,051.5969	$1,051.60	$1,051.60	$1,051.60