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	$62.32	4.150%	$64.9063	$64.91	$64.90	$64.90
Purchase #2	$161.84	11.793%	$180.9258	$180.93	$180.95	$180.90
Purchase #3	$105.38	5.752%	$111.4415	$111.44	$111.45	$111.40
Purchase #4	$56.55	5.241%	$59.5138	$59.51	$59.50	$59.50
Purchase #5	$192.44	5.284%	$202.6085	$202.61	$202.60	$202.60
Purchase #6	$103.72	3.499%	$107.3492	$107.35	$107.35	$107.30
Purchase #7	$245.52	8.169%	$265.5765	$265.58	$265.60	$265.60
7 purchase totals =	$927.77		$992.3216	$992.33	$992.35	$992.20