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	$250.94	4.156%	$261.3691	$261.37	$261.35	$261.40
Purchase #2	$63.41	12.581%	$71.3876	$71.39	$71.40	$71.40
Purchase #3	$130.98	13.678%	$148.8954	$148.90	$148.90	$148.90
Purchase #4	$205.44	5.604%	$216.9529	$216.95	$216.95	$217.00
Purchase #5	$175.92	13.589%	$199.8258	$199.83	$199.85	$199.80
Purchase #6	$110.64	5.637%	$116.8768	$116.88	$116.90	$116.90
Purchase #7	$57.55	6.686%	$61.3978	$61.40	$61.40	$61.40
7 purchase totals =	$994.88		$1,076.7054	$1,076.72	$1,076.75	$1,076.80