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	$232.80	12.571%	$262.0653	$262.07	$262.05	$262.10
Purchase #2	$74.84	10.417%	$82.6361	$82.64	$82.65	$82.60
Purchase #3	$79.43	12.121%	$89.0577	$89.06	$89.05	$89.10
Purchase #4	$189.98	9.589%	$208.1972	$208.20	$208.20	$208.20
Purchase #5	$41.48	8.187%	$44.876	$44.88	$44.90	$44.90
Purchase #6	$166.33	11.459%	$185.3898	$185.39	$185.40	$185.40
Purchase #7	$101.77	3.139%	$104.9646	$104.96	$104.95	$105.00
7 purchase totals =	$886.63		$977.1867	$977.20	$977.20	$977.30