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	$228.52	9.652%	$250.5768	$250.58	$250.60	$250.60
Purchase #2	$157.44	9.145%	$171.8379	$171.84	$171.85	$171.80
Purchase #3	$203.69	3.818%	$211.4669	$211.47	$211.45	$211.50
Purchase #4	$90.25	12.250%	$101.3056	$101.31	$101.30	$101.30
Purchase #5	$229.89	4.817%	$240.9638	$240.96	$240.95	$241.00
Purchase #6	$67.61	7.564%	$72.724	$72.72	$72.70	$72.70
Purchase #7	$15.81	4.522%	$16.5249	$16.52	$16.50	$16.50
7 purchase totals =	$993.21		$1,065.3999	$1,065.40	$1,065.35	$1,065.40