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	$209.88	3.661%	$217.5637	$217.56	$217.55	$217.60
Purchase #2	$67.66	13.638%	$76.8875	$76.89	$76.90	$76.90
Purchase #3	$123.92	5.578%	$130.8323	$130.83	$130.85	$130.80
Purchase #4	$110.90	4.534%	$115.9282	$115.93	$115.95	$115.90
Purchase #5	$81.49	9.312%	$89.0783	$89.08	$89.10	$89.10
Purchase #6	$85.89	12.736%	$96.829	$96.83	$96.85	$96.80
Purchase #7	$182.88	6.377%	$194.5423	$194.54	$194.55	$194.50
7 purchase totals =	$862.62		$921.6613	$921.66	$921.75	$921.60