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	$43.52	6.316%	$46.2687	$46.27	$46.25	$46.30
Purchase #2	$140.63	7.322%	$150.9269	$150.93	$150.95	$150.90
Purchase #3	$43.76	6.783%	$46.7282	$46.73	$46.75	$46.70
Purchase #4	$96.55	7.148%	$103.4514	$103.45	$103.45	$103.50
Purchase #5	$49.94	6.762%	$53.3169	$53.32	$53.30	$53.30
Purchase #6	$246.67	10.633%	$272.8984	$272.90	$272.90	$272.90
Purchase #7	$74.88	13.638%	$85.0921	$85.09	$85.10	$85.10
7 purchase totals =	$695.95		$758.6826	$758.69	$758.70	$758.70