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	$155.32	4.461%	$162.2488	$162.25	$162.25	$162.20
Purchase #2	$178.37	8.686%	$193.8632	$193.86	$193.85	$193.90
Purchase #3	$84.26	13.444%	$95.5879	$95.59	$95.60	$95.60
Purchase #4	$249.51	5.853%	$264.1138	$264.11	$264.10	$264.10
Purchase #5	$96.46	3.750%	$100.0773	$100.08	$100.10	$100.10
Purchase #6	$136.56	4.368%	$142.5249	$142.52	$142.50	$142.50
Purchase #7	$126.36	10.750%	$139.9437	$139.94	$139.95	$139.90
7 purchase totals =	$1,026.84		$1,098.3596	$1,098.35	$1,098.35	$1,098.30