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	$142.25	10.236%	$156.8107	$156.81	$156.80	$156.80
Purchase #2	$102.75	4.837%	$107.72	$107.72	$107.70	$107.70
Purchase #3	$44.67	4.691%	$46.7655	$46.77	$46.75	$46.80
Purchase #4	$98.78	10.745%	$109.3939	$109.39	$109.40	$109.40
Purchase #5	$165.67	10.760%	$183.4961	$183.50	$183.50	$183.50
Purchase #6	$160.80	4.314%	$167.7369	$167.74	$167.75	$167.70
Purchase #7	$249.85	9.465%	$273.4983	$273.50	$273.50	$273.50
7 purchase totals =	$964.77		$1,045.4214	$1,045.43	$1,045.40	$1,045.40