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	$167.64	13.450%	$190.1876	$190.19	$190.20	$190.20
Purchase #2	$25.41	8.387%	$27.5411	$27.54	$27.55	$27.50
Purchase #3	$8.82	7.300%	$9.4639	$9.46	$9.45	$9.50
Purchase #4	$249.49	12.592%	$280.9058	$280.91	$280.90	$280.90
Purchase #5	$94.50	6.623%	$100.7587	$100.76	$100.75	$100.80
Purchase #6	$53.62	11.820%	$59.9579	$59.96	$59.95	$60.00
Purchase #7	$127.66	5.624%	$134.8396	$134.84	$134.85	$134.80
7 purchase totals =	$727.14		$803.6546	$803.66	$803.65	$803.70