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	$46.59	3.279%	$48.1177	$48.12	$48.10	$48.10
Purchase #2	$86.51	3.587%	$89.6131	$89.61	$89.60	$89.60
Purchase #3	$218.81	6.853%	$233.805	$233.81	$233.80	$233.80
Purchase #4	$30.86	3.479%	$31.9336	$31.93	$31.95	$31.90
Purchase #5	$198.60	8.384%	$215.2506	$215.25	$215.25	$215.30
Purchase #6	$65.26	9.283%	$71.3181	$71.32	$71.30	$71.30
Purchase #7	$248.48	4.177%	$258.859	$258.86	$258.85	$258.90
7 purchase totals =	$895.11		$948.8971	$948.90	$948.85	$948.90