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	$70.86	3.213%	$73.1367	$73.14	$73.15	$73.10
Purchase #2	$71.71	6.853%	$76.6243	$76.62	$76.60	$76.60
Purchase #3	$180.79	8.648%	$196.4247	$196.42	$196.40	$196.40
Purchase #4	$152.51	9.795%	$167.4484	$167.45	$167.45	$167.40
Purchase #5	$86.67	3.820%	$89.9808	$89.98	$90.00	$90.00
Purchase #6	$172.82	12.372%	$194.2013	$194.20	$194.20	$194.20
Purchase #7	$114.72	11.713%	$128.1572	$128.16	$128.15	$128.20
7 purchase totals =	$850.08		$925.9734	$925.97	$925.95	$925.90