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	$41.71	10.481%	$46.0816	$46.08	$46.10	$46.10
Purchase #2	$139.69	6.219%	$148.3773	$148.38	$148.40	$148.40
Purchase #3	$133.78	12.142%	$150.0236	$150.02	$150.00	$150.00
Purchase #4	$12.40	9.836%	$13.6197	$13.62	$13.60	$13.60
Purchase #5	$213.25	4.249%	$222.311	$222.31	$222.30	$222.30
Purchase #6	$183.27	5.276%	$192.9393	$192.94	$192.95	$192.90
Purchase #7	$68.60	5.127%	$72.1171	$72.12	$72.10	$72.10
7 purchase totals =	$792.70		$845.4696	$845.47	$845.45	$845.40