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	$156.37	11.320%	$174.0711	$174.07	$174.05	$174.10
Purchase #2	$113.72	8.281%	$123.1372	$123.14	$123.15	$123.10
Purchase #3	$10.31	10.137%	$11.3551	$11.36	$11.35	$11.40
Purchase #4	$44.45	6.457%	$47.3201	$47.32	$47.30	$47.30
Purchase #5	$75.59	3.268%	$78.0603	$78.06	$78.05	$78.10
Purchase #6	$74.51	10.718%	$82.496	$82.50	$82.50	$82.50
Purchase #7	$113.81	6.652%	$121.3806	$121.38	$121.40	$121.40
7 purchase totals =	$588.76		$637.8204	$637.83	$637.80	$637.90