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	$135.59	4.370%	$141.5153	$141.52	$141.50	$141.50
Purchase #2	$177.97	13.136%	$201.3481	$201.35	$201.35	$201.30
Purchase #3	$25.83	5.375%	$27.2184	$27.22	$27.20	$27.20
Purchase #4	$104.88	5.183%	$110.3159	$110.32	$110.30	$110.30
Purchase #5	$64.34	11.759%	$71.9057	$71.91	$71.90	$71.90
Purchase #6	$105.96	5.144%	$111.4106	$111.41	$111.40	$111.40
Purchase #7	$51.46	4.697%	$53.8771	$53.88	$53.90	$53.90
7 purchase totals =	$666.03		$717.5911	$717.61	$717.55	$717.50