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	$44.43	7.517%	$47.7698	$47.77	$47.75	$47.80
Purchase #2	$245.39	12.495%	$276.0515	$276.05	$276.05	$276.10
Purchase #3	$242.47	8.574%	$263.2594	$263.26	$263.25	$263.30
Purchase #4	$118.69	6.627%	$126.5556	$126.56	$126.55	$126.60
Purchase #5	$118.64	10.467%	$131.058	$131.06	$131.05	$131.10
Purchase #6	$187.94	4.558%	$196.5063	$196.51	$196.50	$196.50
Purchase #7	$62.94	6.807%	$67.2243	$67.22	$67.20	$67.20
7 purchase totals =	$1,020.50		$1,108.4249	$1,108.43	$1,108.35	$1,108.60