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	$204.90	8.517%	$222.3513	$222.35	$222.35	$222.40
Purchase #2	$176.56	6.661%	$188.3207	$188.32	$188.30	$188.30
Purchase #3	$114.68	12.615%	$129.1469	$129.15	$129.15	$129.10
Purchase #4	$39.86	8.572%	$43.2768	$43.28	$43.30	$43.30
Purchase #5	$200.74	10.360%	$221.5367	$221.54	$221.55	$221.50
Purchase #6	$39.98	9.345%	$43.7161	$43.72	$43.70	$43.70
Purchase #7	$249.96	5.795%	$264.4452	$264.45	$264.45	$264.40
7 purchase totals =	$1,026.68		$1,112.7937	$1,112.81	$1,112.80	$1,112.70