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	$54.72	12.646%	$61.6399	$61.64	$61.65	$61.60
Purchase #2	$118.56	8.619%	$128.7787	$128.78	$128.80	$128.80
Purchase #3	$55.86	11.118%	$62.0705	$62.07	$62.05	$62.10
Purchase #4	$222.29	9.576%	$243.5765	$243.58	$243.60	$243.60
Purchase #5	$6.40	8.124%	$6.9199	$6.92	$6.90	$6.90
Purchase #6	$155.30	4.649%	$162.5199	$162.52	$162.50	$162.50
Purchase #7	$30.99	4.623%	$32.4227	$32.42	$32.40	$32.40
7 purchase totals =	$644.12		$697.9281	$697.93	$697.90	$697.90