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	$64.53	10.129%	$71.0662	$71.07	$71.05	$71.10
Purchase #2	$235.58	13.272%	$266.8462	$266.85	$266.85	$266.80
Purchase #3	$172.60	12.512%	$194.1957	$194.20	$194.20	$194.20
Purchase #4	$171.40	12.779%	$193.3032	$193.30	$193.30	$193.30
Purchase #5	$249.61	5.678%	$263.7829	$263.78	$263.80	$263.80
Purchase #6	$157.35	6.447%	$167.4944	$167.49	$167.50	$167.50
Purchase #7	$38.93	3.155%	$40.1582	$40.16	$40.15	$40.20
7 purchase totals =	$1,090.00		$1,196.8468	$1,196.85	$1,196.85	$1,196.90