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	$116.83	11.745%	$130.5517	$130.55	$130.55	$130.60
Purchase #2	$101.63	9.226%	$111.0064	$111.01	$111.00	$111.00
Purchase #3	$53.41	4.270%	$55.6906	$55.69	$55.70	$55.70
Purchase #4	$203.55	13.553%	$231.1371	$231.14	$231.15	$231.10
Purchase #5	$29.98	5.431%	$31.6082	$31.61	$31.60	$31.60
Purchase #6	$82.67	11.240%	$91.9621	$91.96	$91.95	$92.00
Purchase #7	$150.79	13.434%	$171.0471	$171.05	$171.05	$171.00
7 purchase totals =	$738.86		$823.0032	$823.01	$823.00	$823.00