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	$160.85	11.214%	$178.8877	$178.89	$178.90	$178.90
Purchase #2	$83.88	12.138%	$94.0614	$94.06	$94.05	$94.10
Purchase #3	$223.98	8.611%	$243.2669	$243.27	$243.25	$243.30
Purchase #4	$160.33	9.314%	$175.2631	$175.26	$175.25	$175.30
Purchase #5	$38.29	10.453%	$42.2925	$42.29	$42.30	$42.30
Purchase #6	$179.63	5.797%	$190.0432	$190.04	$190.05	$190.00
Purchase #7	$69.76	4.291%	$72.7534	$72.75	$72.75	$72.80
7 purchase totals =	$916.72		$996.5682	$996.56	$996.55	$996.70