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	$167.84	4.466%	$175.3357	$175.34	$175.35	$175.30
Purchase #2	$88.97	7.468%	$95.6143	$95.61	$95.60	$95.60
Purchase #3	$174.89	7.531%	$188.061	$188.06	$188.05	$188.10
Purchase #4	$199.59	12.462%	$224.4629	$224.46	$224.45	$224.50
Purchase #5	$89.87	10.705%	$99.4906	$99.49	$99.50	$99.50
Purchase #6	$28.62	8.482%	$31.0475	$31.05	$31.05	$31.00
Purchase #7	$175.38	5.645%	$185.2802	$185.28	$185.30	$185.30
7 purchase totals =	$925.16		$999.2922	$999.29	$999.30	$999.30