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	$41.71	10.138%	$45.9386	$45.94	$45.95	$45.90
Purchase #2	$125.55	8.638%	$136.395	$136.40	$136.40	$136.40
Purchase #3	$80.76	8.849%	$87.9065	$87.91	$87.90	$87.90
Purchase #4	$78.35	4.805%	$82.1147	$82.11	$82.10	$82.10
Purchase #5	$162.80	3.554%	$168.5859	$168.59	$168.60	$168.60
Purchase #6	$149.40	7.322%	$160.3391	$160.34	$160.35	$160.30
Purchase #7	$158.61	3.846%	$164.7101	$164.71	$164.70	$164.70
7 purchase totals =	$797.18		$845.9899	$846.00	$846.00	$845.90