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	$229.48	5.415%	$241.9063	$241.91	$241.90	$241.90
Purchase #2	$170.97	8.314%	$185.1844	$185.18	$185.20	$185.20
Purchase #3	$144.30	12.278%	$162.0172	$162.02	$162.00	$162.00
Purchase #4	$225.69	10.503%	$249.3942	$249.39	$249.40	$249.40
Purchase #5	$158.73	13.725%	$180.5157	$180.52	$180.50	$180.50
Purchase #6	$67.73	12.787%	$76.3906	$76.39	$76.40	$76.40
Purchase #7	$182.83	4.211%	$190.529	$190.53	$190.55	$190.50
7 purchase totals =	$1,179.73		$1,285.9374	$1,285.94	$1,285.95	$1,285.90