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	$95.49	8.721%	$103.8177	$103.82	$103.80	$103.80
Purchase #2	$73.52	12.118%	$82.4292	$82.43	$82.45	$82.40
Purchase #3	$179.50	13.171%	$203.1419	$203.14	$203.15	$203.10
Purchase #4	$42.30	4.526%	$44.2145	$44.21	$44.20	$44.20
Purchase #5	$195.86	3.149%	$202.0276	$202.03	$202.05	$202.00
Purchase #6	$179.83	9.171%	$196.3222	$196.32	$196.30	$196.30
Purchase #7	$174.26	11.588%	$194.4532	$194.45	$194.45	$194.50
7 purchase totals =	$940.76		$1,026.4063	$1,026.40	$1,026.40	$1,026.30