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	$57.87	11.765%	$64.6784	$64.68	$64.70	$64.70
Purchase #2	$95.72	4.298%	$99.834	$99.83	$99.85	$99.80
Purchase #3	$37.48	12.317%	$42.0964	$42.10	$42.10	$42.10
Purchase #4	$39.76	7.315%	$42.6684	$42.67	$42.65	$42.70
Purchase #5	$33.62	5.307%	$35.4042	$35.40	$35.40	$35.40
Purchase #6	$156.52	11.855%	$175.0754	$175.08	$175.10	$175.10
Purchase #7	$166.54	6.264%	$176.9721	$176.97	$176.95	$177.00
7 purchase totals =	$587.51		$636.7289	$636.73	$636.75	$636.80