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	$97.40	5.835%	$103.0833	$103.08	$103.10	$103.10
Purchase #2	$123.80	7.265%	$132.7941	$132.79	$132.80	$132.80
Purchase #3	$57.48	5.287%	$60.519	$60.52	$60.50	$60.50
Purchase #4	$120.54	10.134%	$132.7555	$132.76	$132.75	$132.80
Purchase #5	$79.52	3.122%	$82.0026	$82.00	$82.00	$82.00
Purchase #6	$115.96	7.649%	$124.8298	$124.83	$124.85	$124.80
Purchase #7	$65.32	3.216%	$67.4207	$67.42	$67.40	$67.40
7 purchase totals =	$660.02		$703.4050	$703.40	$703.40	$703.40