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	$68.64	10.855%	$76.0909	$76.09	$76.10	$76.10
Purchase #2	$250.86	5.258%	$264.0502	$264.05	$264.05	$264.10
Purchase #3	$9.38	10.661%	$10.38	$10.38	$10.40	$10.40
Purchase #4	$160.57	8.748%	$174.6167	$174.62	$174.60	$174.60
Purchase #5	$250.86	6.870%	$268.0941	$268.09	$268.10	$268.10
Purchase #6	$227.34	10.597%	$251.4312	$251.43	$251.45	$251.40
Purchase #7	$42.77	6.430%	$45.5201	$45.52	$45.50	$45.50
7 purchase totals =	$1,010.42		$1,090.1832	$1,090.18	$1,090.20	$1,090.20