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	$150.58	3.745%	$156.2192	$156.22	$156.20	$156.20
Purchase #2	$152.92	3.396%	$158.1132	$158.11	$158.10	$158.10
Purchase #3	$130.46	13.664%	$148.2861	$148.29	$148.30	$148.30
Purchase #4	$140.51	5.624%	$148.4123	$148.41	$148.40	$148.40
Purchase #5	$67.37	9.495%	$73.7668	$73.77	$73.75	$73.80
Purchase #6	$39.79	7.774%	$42.8833	$42.88	$42.90	$42.90
Purchase #7	$208.36	3.587%	$215.8339	$215.83	$215.85	$215.80
7 purchase totals =	$889.99		$943.5148	$943.51	$943.50	$943.50