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	$53.90	9.578%	$59.0625	$59.06	$59.05	$59.10
Purchase #2	$85.27	7.801%	$91.9219	$91.92	$91.90	$91.90
Purchase #3	$28.98	8.868%	$31.5499	$31.55	$31.55	$31.50
Purchase #4	$135.71	4.464%	$141.7681	$141.77	$141.75	$141.80
Purchase #5	$59.95	7.835%	$64.6471	$64.65	$64.65	$64.60
Purchase #6	$158.94	4.537%	$166.1511	$166.15	$166.15	$166.20
Purchase #7	$233.29	6.808%	$249.1724	$249.17	$249.15	$249.20
7 purchase totals =	$756.04		$804.2730	$804.27	$804.20	$804.30