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	$181.61	10.482%	$200.6464	$200.65	$200.65	$200.60
Purchase #2	$214.98	3.690%	$222.9128	$222.91	$222.90	$222.90
Purchase #3	$136.34	9.228%	$148.9215	$148.92	$148.90	$148.90
Purchase #4	$75.31	8.109%	$81.4169	$81.42	$81.40	$81.40
Purchase #5	$146.31	11.448%	$163.0596	$163.06	$163.05	$163.10
Purchase #6	$178.81	5.327%	$188.3352	$188.34	$188.35	$188.30
Purchase #7	$51.85	7.204%	$55.5853	$55.59	$55.60	$55.60
7 purchase totals =	$985.21		$1,060.8777	$1,060.89	$1,060.85	$1,060.80