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	$59.45	4.683%	$62.234	$62.23	$62.25	$62.20
Purchase #2	$233.91	3.280%	$241.5822	$241.58	$241.60	$241.60
Purchase #3	$36.46	11.344%	$40.596	$40.60	$40.60	$40.60
Purchase #4	$59.98	13.604%	$68.1397	$68.14	$68.15	$68.10
Purchase #5	$61.60	5.236%	$64.8254	$64.83	$64.85	$64.80
Purchase #6	$196.54	8.560%	$213.3638	$213.36	$213.35	$213.40
Purchase #7	$194.88	7.803%	$210.0865	$210.09	$210.10	$210.10
7 purchase totals =	$842.82		$900.8276	$900.83	$900.90	$900.80