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	$229.77	6.317%	$244.2846	$244.28	$244.30	$244.30
Purchase #2	$38.77	12.240%	$43.5154	$43.52	$43.50	$43.50
Purchase #3	$227.53	5.198%	$239.357	$239.36	$239.35	$239.40
Purchase #4	$78.76	4.745%	$82.4972	$82.50	$82.50	$82.50
Purchase #5	$176.63	12.617%	$198.9154	$198.92	$198.90	$198.90
Purchase #6	$164.72	5.240%	$173.3513	$173.35	$173.35	$173.40
Purchase #7	$65.50	7.190%	$70.2095	$70.21	$70.20	$70.20
7 purchase totals =	$981.68		$1,052.1304	$1,052.14	$1,052.10	$1,052.20