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	$67.77	7.371%	$72.7653	$72.77	$72.75	$72.80
Purchase #2	$236.53	8.141%	$255.7859	$255.79	$255.80	$255.80
Purchase #3	$94.62	5.201%	$99.5412	$99.54	$99.55	$99.50
Purchase #4	$136.60	9.618%	$149.7382	$149.74	$149.75	$149.70
Purchase #5	$194.76	9.558%	$213.3752	$213.38	$213.40	$213.40
Purchase #6	$61.95	12.823%	$69.8938	$69.89	$69.90	$69.90
Purchase #7	$231.77	3.180%	$239.1403	$239.14	$239.15	$239.10
7 purchase totals =	$1,024.00		$1,100.2399	$1,100.25	$1,100.30	$1,100.20