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	$66.39	7.771%	$71.5492	$71.55	$71.55	$71.50
Purchase #2	$78.62	11.678%	$87.8012	$87.80	$87.80	$87.80
Purchase #3	$19.82	12.280%	$22.2539	$22.25	$22.25	$22.30
Purchase #4	$104.97	12.824%	$118.4314	$118.43	$118.45	$118.40
Purchase #5	$68.27	3.119%	$70.3993	$70.40	$70.40	$70.40
Purchase #6	$157.53	6.846%	$168.3145	$168.31	$168.30	$168.30
Purchase #7	$224.84	11.123%	$249.849	$249.85	$249.85	$249.80
7 purchase totals =	$720.44		$788.5985	$788.59	$788.60	$788.50