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	$139.38	13.853%	$158.6883	$158.69	$158.70	$158.70
Purchase #2	$7.50	12.416%	$8.4312	$8.43	$8.45	$8.40
Purchase #3	$168.39	3.519%	$174.3156	$174.32	$174.30	$174.30
Purchase #4	$62.93	13.269%	$71.2802	$71.28	$71.30	$71.30
Purchase #5	$225.92	3.303%	$233.3821	$233.38	$233.40	$233.40
Purchase #6	$194.51	11.821%	$217.503	$217.50	$217.50	$217.50
Purchase #7	$213.36	11.211%	$237.2798	$237.28	$237.30	$237.30
7 purchase totals =	$1,011.99		$1,100.8802	$1,100.88	$1,100.95	$1,100.90