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	$148.69	8.225%	$160.9198	$160.92	$160.90	$160.90
Purchase #2	$223.52	4.841%	$234.3406	$234.34	$234.35	$234.30
Purchase #3	$67.98	7.304%	$72.9453	$72.95	$72.95	$72.90
Purchase #4	$208.30	4.795%	$218.288	$218.29	$218.30	$218.30
Purchase #5	$20.94	4.791%	$21.9432	$21.94	$21.95	$21.90
Purchase #6	$91.44	6.545%	$97.4247	$97.42	$97.40	$97.40
Purchase #7	$248.93	8.757%	$270.7288	$270.73	$270.75	$270.70
7 purchase totals =	$1,009.80		$1,076.5904	$1,076.59	$1,076.60	$1,076.40