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	$45.86	3.328%	$47.3862	$47.39	$47.40	$47.40
Purchase #2	$56.56	13.629%	$64.2686	$64.27	$64.25	$64.30
Purchase #3	$215.91	13.685%	$245.4573	$245.46	$245.45	$245.50
Purchase #4	$115.72	10.566%	$127.947	$127.95	$127.95	$127.90
Purchase #5	$208.39	8.708%	$226.5366	$226.54	$226.55	$226.50
Purchase #6	$139.61	9.364%	$152.6831	$152.68	$152.70	$152.70
Purchase #7	$176.83	12.344%	$198.6579	$198.66	$198.65	$198.70
7 purchase totals =	$958.88		$1,062.9367	$1,062.95	$1,062.95	$1,063.00