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	$246.83	7.309%	$264.8708	$264.87	$264.85	$264.90
Purchase #2	$167.82	10.773%	$185.8992	$185.90	$185.90	$185.90
Purchase #3	$52.62	9.765%	$57.7583	$57.76	$57.75	$57.80
Purchase #4	$82.70	8.441%	$89.6807	$89.68	$89.70	$89.70
Purchase #5	$220.42	3.195%	$227.4624	$227.46	$227.45	$227.50
Purchase #6	$105.84	11.587%	$118.1037	$118.10	$118.10	$118.10
Purchase #7	$45.44	6.815%	$48.5367	$48.54	$48.55	$48.50
7 purchase totals =	$921.67		$992.3118	$992.31	$992.30	$992.40