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	$142.87	9.721%	$156.7584	$156.76	$156.75	$156.80
Purchase #2	$196.37	13.383%	$222.6502	$222.65	$222.65	$222.70
Purchase #3	$31.78	10.153%	$35.0066	$35.01	$35.00	$35.00
Purchase #4	$54.89	12.137%	$61.552	$61.55	$61.55	$61.60
Purchase #5	$59.54	13.177%	$67.3856	$67.39	$67.40	$67.40
Purchase #6	$114.65	4.351%	$119.6384	$119.64	$119.65	$119.60
Purchase #7	$53.27	13.150%	$60.275	$60.28	$60.30	$60.30
7 purchase totals =	$653.37		$723.2662	$723.28	$723.30	$723.40