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	$233.31	12.492%	$262.4551	$262.46	$262.45	$262.50
Purchase #2	$56.74	9.450%	$62.1019	$62.10	$62.10	$62.10
Purchase #3	$99.26	5.661%	$104.8791	$104.88	$104.90	$104.90
Purchase #4	$225.33	7.154%	$241.4501	$241.45	$241.45	$241.50
Purchase #5	$232.31	7.659%	$250.1026	$250.10	$250.10	$250.10
Purchase #6	$117.66	5.279%	$123.8713	$123.87	$123.85	$123.90
Purchase #7	$231.80	7.685%	$249.6138	$249.61	$249.60	$249.60
7 purchase totals =	$1,196.41		$1,294.4739	$1,294.47	$1,294.45	$1,294.60