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	$196.62	12.372%	$220.9458	$220.95	$220.95	$220.90
Purchase #2	$136.48	4.742%	$142.9519	$142.95	$142.95	$143.00
Purchase #3	$41.73	9.549%	$45.7148	$45.71	$45.70	$45.70
Purchase #4	$47.43	10.836%	$52.5695	$52.57	$52.55	$52.60
Purchase #5	$19.51	5.320%	$20.5479	$20.55	$20.55	$20.50
Purchase #6	$31.50	7.163%	$33.7563	$33.76	$33.75	$33.80
Purchase #7	$39.71	10.474%	$43.8692	$43.87	$43.85	$43.90
7 purchase totals =	$512.98		$560.3554	$560.36	$560.30	$560.40