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	$65.47	3.521%	$67.7752	$67.78	$67.80	$67.80
Purchase #2	$80.37	11.580%	$89.6768	$89.68	$89.70	$89.70
Purchase #3	$115.81	8.127%	$125.2219	$125.22	$125.20	$125.20
Purchase #4	$239.78	10.338%	$264.5685	$264.57	$264.55	$264.60
Purchase #5	$204.51	3.197%	$211.0482	$211.05	$211.05	$211.00
Purchase #6	$85.84	11.337%	$95.5717	$95.57	$95.55	$95.60
Purchase #7	$108.55	13.698%	$123.4192	$123.42	$123.40	$123.40
7 purchase totals =	$900.33		$977.2815	$977.29	$977.25	$977.30