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	$102.85	7.504%	$110.5679	$110.57	$110.55	$110.60
Purchase #2	$132.34	13.554%	$150.2774	$150.28	$150.30	$150.30
Purchase #3	$184.86	3.249%	$190.8661	$190.87	$190.85	$190.90
Purchase #4	$188.25	9.490%	$206.1149	$206.11	$206.10	$206.10
Purchase #5	$25.35	7.844%	$27.3385	$27.34	$27.35	$27.30
Purchase #6	$201.33	7.446%	$216.321	$216.32	$216.30	$216.30
Purchase #7	$111.95	13.830%	$127.4327	$127.43	$127.45	$127.40
7 purchase totals =	$946.93		$1,028.9185	$1,028.92	$1,028.90	$1,028.90