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	$101.78	11.212%	$113.1916	$113.19	$113.20	$113.20
Purchase #2	$206.90	7.648%	$222.7237	$222.72	$222.70	$222.70
Purchase #3	$43.95	7.821%	$47.3873	$47.39	$47.40	$47.40
Purchase #4	$60.40	6.195%	$64.1418	$64.14	$64.15	$64.10
Purchase #5	$127.80	11.307%	$142.2503	$142.25	$142.25	$142.30
Purchase #6	$98.83	7.401%	$106.1444	$106.14	$106.15	$106.10
Purchase #7	$143.93	6.255%	$152.9328	$152.93	$152.95	$152.90
7 purchase totals =	$783.59		$848.7719	$848.76	$848.80	$848.70