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	$148.31	9.751%	$162.7717	$162.77	$162.75	$162.80
Purchase #2	$47.32	12.832%	$53.3921	$53.39	$53.40	$53.40
Purchase #3	$60.82	10.573%	$67.2505	$67.25	$67.25	$67.30
Purchase #4	$124.82	5.645%	$131.8661	$131.87	$131.85	$131.90
Purchase #5	$195.90	9.827%	$215.1511	$215.15	$215.15	$215.20
Purchase #6	$138.64	11.797%	$154.9954	$155.00	$155.00	$155.00
Purchase #7	$87.63	12.449%	$98.5391	$98.54	$98.55	$98.50
7 purchase totals =	$803.44		$883.9660	$883.97	$883.95	$884.10