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	$98.60	10.752%	$109.2015	$109.20	$109.20	$109.20
Purchase #2	$56.34	5.440%	$59.4049	$59.40	$59.40	$59.40
Purchase #3	$81.30	10.390%	$89.7471	$89.75	$89.75	$89.70
Purchase #4	$86.42	9.795%	$94.8848	$94.88	$94.90	$94.90
Purchase #5	$218.60	7.241%	$234.4288	$234.43	$234.45	$234.40
Purchase #6	$230.26	8.864%	$250.6702	$250.67	$250.65	$250.70
Purchase #7	$227.76	4.351%	$237.6698	$237.67	$237.65	$237.70
7 purchase totals =	$999.28		$1,076.0071	$1,076.00	$1,076.00	$1,076.00