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	$171.76	7.446%	$184.5492	$184.55	$184.55	$184.50
Purchase #2	$152.35	10.547%	$168.4184	$168.42	$168.40	$168.40
Purchase #3	$90.91	10.640%	$100.5828	$100.58	$100.60	$100.60
Purchase #4	$201.32	6.564%	$214.5346	$214.53	$214.55	$214.50
Purchase #5	$6.81	8.629%	$7.3976	$7.40	$7.40	$7.40
Purchase #6	$101.59	13.294%	$115.0954	$115.10	$115.10	$115.10
Purchase #7	$184.77	6.400%	$196.5953	$196.60	$196.60	$196.60
7 purchase totals =	$909.51		$987.1733	$987.18	$987.20	$987.10