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	$5.28	11.770%	$5.9015	$5.90	$5.90	$5.90
Purchase #2	$148.27	5.544%	$156.4901	$156.49	$156.50	$156.50
Purchase #3	$204.63	3.515%	$211.8227	$211.82	$211.80	$211.80
Purchase #4	$150.63	10.352%	$166.2232	$166.22	$166.20	$166.20
Purchase #5	$163.58	10.427%	$180.6365	$180.64	$180.65	$180.60
Purchase #6	$211.27	4.310%	$220.3757	$220.38	$220.40	$220.40
Purchase #7	$129.58	11.810%	$144.8834	$144.88	$144.90	$144.90
7 purchase totals =	$1,013.24		$1,086.3331	$1,086.33	$1,086.35	$1,086.30