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	$134.30	12.459%	$151.0324	$151.03	$151.05	$151.00
Purchase #2	$70.48	3.506%	$72.951	$72.95	$72.95	$73.00
Purchase #3	$61.94	5.440%	$65.3095	$65.31	$65.30	$65.30
Purchase #4	$6.95	13.379%	$7.8798	$7.88	$7.90	$7.90
Purchase #5	$85.38	6.184%	$90.6599	$90.66	$90.65	$90.70
Purchase #6	$11.98	13.416%	$13.5872	$13.59	$13.60	$13.60
Purchase #7	$6.98	5.392%	$7.3564	$7.36	$7.35	$7.40
7 purchase totals =	$378.01		$408.7762	$408.78	$408.80	$408.90