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	$107.95	4.331%	$112.6253	$112.63	$112.65	$112.60
Purchase #2	$94.44	5.419%	$99.5577	$99.56	$99.55	$99.60
Purchase #3	$35.89	6.643%	$38.2742	$38.27	$38.25	$38.30
Purchase #4	$180.96	8.675%	$196.6583	$196.66	$196.65	$196.70
Purchase #5	$47.35	12.562%	$53.2981	$53.30	$53.30	$53.30
Purchase #6	$250.51	6.589%	$267.0161	$267.02	$267.00	$267.00
Purchase #7	$105.64	6.385%	$112.3851	$112.39	$112.40	$112.40
7 purchase totals =	$822.74		$879.8148	$879.83	$879.80	$879.90