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	$135.40	8.623%	$147.0755	$147.08	$147.10	$147.10
Purchase #2	$144.79	13.790%	$164.7565	$164.76	$164.75	$164.80
Purchase #3	$82.29	8.614%	$89.3785	$89.38	$89.40	$89.40
Purchase #4	$188.62	3.182%	$194.6219	$194.62	$194.60	$194.60
Purchase #5	$232.26	13.142%	$262.7836	$262.78	$262.80	$262.80
Purchase #6	$190.29	13.589%	$216.1485	$216.15	$216.15	$216.10
Purchase #7	$41.49	5.418%	$43.7379	$43.74	$43.75	$43.70
7 purchase totals =	$1,015.14		$1,118.5024	$1,118.51	$1,118.55	$1,118.50