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	$125.78	12.127%	$141.0333	$141.03	$141.05	$141.00
Purchase #2	$142.35	3.445%	$147.254	$147.25	$147.25	$147.30
Purchase #3	$97.45	6.482%	$103.7667	$103.77	$103.75	$103.80
Purchase #4	$241.79	9.275%	$264.216	$264.22	$264.20	$264.20
Purchase #5	$223.31	9.245%	$243.955	$243.96	$243.95	$244.00
Purchase #6	$244.50	10.639%	$270.5124	$270.51	$270.50	$270.50
Purchase #7	$228.31	5.525%	$240.9241	$240.92	$240.90	$240.90
7 purchase totals =	$1,303.49		$1,411.6615	$1,411.66	$1,411.60	$1,411.70