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	$63.41	6.114%	$67.2869	$67.29	$67.30	$67.30
Purchase #2	$200.73	3.574%	$207.9041	$207.90	$207.90	$207.90
Purchase #3	$72.62	13.534%	$82.4484	$82.45	$82.45	$82.40
Purchase #4	$67.26	7.707%	$72.4437	$72.44	$72.45	$72.40
Purchase #5	$92.46	4.256%	$96.3951	$96.40	$96.40	$96.40
Purchase #6	$148.64	6.352%	$158.0816	$158.08	$158.10	$158.10
Purchase #7	$76.71	4.382%	$80.0714	$80.07	$80.05	$80.10
7 purchase totals =	$721.83		$764.6312	$764.63	$764.65	$764.60