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	$137.62	9.841%	$151.1632	$151.16	$151.15	$151.20
Purchase #2	$149.42	10.359%	$164.8984	$164.90	$164.90	$164.90
Purchase #3	$27.63	5.316%	$29.0988	$29.10	$29.10	$29.10
Purchase #4	$75.90	3.448%	$78.517	$78.52	$78.50	$78.50
Purchase #5	$111.57	3.417%	$115.3823	$115.38	$115.40	$115.40
Purchase #6	$53.51	5.790%	$56.6082	$56.61	$56.60	$56.60
Purchase #7	$231.67	4.528%	$242.16	$242.16	$242.15	$242.20
7 purchase totals =	$787.32		$837.8279	$837.83	$837.80	$837.90