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	$54.32	4.275%	$56.6422	$56.64	$56.65	$56.60
Purchase #2	$201.44	7.786%	$217.1241	$217.12	$217.10	$217.10
Purchase #3	$127.81	7.799%	$137.7779	$137.78	$137.80	$137.80
Purchase #4	$122.76	8.602%	$133.3198	$133.32	$133.30	$133.30
Purchase #5	$36.59	4.200%	$38.1268	$38.13	$38.15	$38.10
Purchase #6	$229.74	9.211%	$250.9014	$250.90	$250.90	$250.90
Purchase #7	$153.37	10.231%	$169.0613	$169.06	$169.05	$169.10
7 purchase totals =	$926.03		$1,002.9535	$1,002.95	$1,002.95	$1,002.90