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	$248.31	13.797%	$282.5693	$282.57	$282.55	$282.60
Purchase #2	$206.41	11.780%	$230.7251	$230.73	$230.75	$230.70
Purchase #3	$64.35	10.835%	$71.3223	$71.32	$71.30	$71.30
Purchase #4	$178.95	6.510%	$190.5996	$190.60	$190.60	$190.60
Purchase #5	$187.86	13.646%	$213.4954	$213.50	$213.50	$213.50
Purchase #6	$242.74	5.524%	$256.149	$256.15	$256.15	$256.10
Purchase #7	$105.79	4.432%	$110.4786	$110.48	$110.50	$110.50
7 purchase totals =	$1,234.41		$1,355.3393	$1,355.35	$1,355.35	$1,355.30