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	$57.86	11.518%	$64.5243	$64.52	$64.50	$64.50
Purchase #2	$127.65	9.560%	$139.8533	$139.85	$139.85	$139.90
Purchase #3	$152.47	7.861%	$164.4557	$164.46	$164.45	$164.50
Purchase #4	$187.86	4.501%	$196.3156	$196.32	$196.30	$196.30
Purchase #5	$199.77	4.234%	$208.2283	$208.23	$208.25	$208.20
Purchase #6	$167.84	5.616%	$177.2659	$177.27	$177.25	$177.30
Purchase #7	$228.47	6.503%	$243.3274	$243.33	$243.35	$243.30
7 purchase totals =	$1,121.92		$1,193.9705	$1,193.98	$1,193.95	$1,194.00