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	$142.74	5.294%	$150.2967	$150.30	$150.30	$150.30
Purchase #2	$83.82	6.267%	$89.073	$89.07	$89.05	$89.10
Purchase #3	$73.31	12.542%	$82.5045	$82.50	$82.50	$82.50
Purchase #4	$241.41	4.159%	$251.4502	$251.45	$251.45	$251.50
Purchase #5	$96.37	4.871%	$101.0642	$101.06	$101.05	$101.10
Purchase #6	$209.59	10.727%	$232.0727	$232.07	$232.05	$232.10
Purchase #7	$17.73	9.595%	$19.4312	$19.43	$19.45	$19.40
7 purchase totals =	$864.97		$925.8925	$925.88	$925.85	$926.00