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	$23.48	9.567%	$25.7263	$25.73	$25.75	$25.70
Purchase #2	$26.92	7.356%	$28.9002	$28.90	$28.90	$28.90
Purchase #3	$42.56	4.604%	$44.5195	$44.52	$44.50	$44.50
Purchase #4	$39.96	6.236%	$42.4519	$42.45	$42.45	$42.50
Purchase #5	$97.79	3.201%	$100.9203	$100.92	$100.90	$100.90
Purchase #6	$183.88	6.852%	$196.4795	$196.48	$196.50	$196.50
Purchase #7	$216.33	12.687%	$243.7758	$243.78	$243.80	$243.80
7 purchase totals =	$630.92		$682.7735	$682.78	$682.80	$682.80