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	$53.97	9.740%	$59.2267	$59.23	$59.25	$59.20
Purchase #2	$122.93	3.265%	$126.9437	$126.94	$126.95	$126.90
Purchase #3	$249.50	6.167%	$264.8867	$264.89	$264.90	$264.90
Purchase #4	$64.85	5.652%	$68.5153	$68.52	$68.50	$68.50
Purchase #5	$82.34	8.689%	$89.4945	$89.49	$89.50	$89.50
Purchase #6	$66.33	13.662%	$75.392	$75.39	$75.40	$75.40
Purchase #7	$89.92	12.204%	$100.8938	$100.89	$100.90	$100.90
7 purchase totals =	$729.84		$785.3527	$785.35	$785.40	$785.30