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	$210.76	11.528%	$235.0564	$235.06	$235.05	$235.10
Purchase #2	$192.49	11.474%	$214.5763	$214.58	$214.60	$214.60
Purchase #3	$85.71	4.519%	$89.5832	$89.58	$89.60	$89.60
Purchase #4	$38.33	8.872%	$41.7306	$41.73	$41.75	$41.70
Purchase #5	$39.80	12.367%	$44.7221	$44.72	$44.70	$44.70
Purchase #6	$81.65	12.125%	$91.5501	$91.55	$91.55	$91.60
Purchase #7	$85.63	5.289%	$90.159	$90.16	$90.15	$90.20
7 purchase totals =	$734.37		$807.3777	$807.38	$807.40	$807.50