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	$57.80	4.733%	$60.5357	$60.54	$60.55	$60.50
Purchase #2	$98.82	11.733%	$110.4146	$110.41	$110.40	$110.40
Purchase #3	$190.32	11.316%	$211.8566	$211.86	$211.85	$211.90
Purchase #4	$118.25	13.271%	$133.943	$133.94	$133.95	$133.90
Purchase #5	$187.69	4.586%	$196.2975	$196.30	$196.30	$196.30
Purchase #6	$122.55	7.326%	$131.528	$131.53	$131.55	$131.50
Purchase #7	$196.80	6.303%	$209.2043	$209.20	$209.20	$209.20
7 purchase totals =	$972.23		$1,053.7797	$1,053.78	$1,053.80	$1,053.70