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	$207.48	11.552%	$231.4481	$231.45	$231.45	$231.40
Purchase #2	$156.45	6.385%	$166.4393	$166.44	$166.45	$166.40
Purchase #3	$212.98	4.538%	$222.645	$222.65	$222.65	$222.60
Purchase #4	$144.91	3.670%	$150.2282	$150.23	$150.25	$150.20
Purchase #5	$245.33	4.437%	$256.2153	$256.22	$256.20	$256.20
Purchase #6	$45.82	13.108%	$51.8261	$51.83	$51.85	$51.80
Purchase #7	$33.35	13.302%	$37.7862	$37.79	$37.80	$37.80
7 purchase totals =	$1,046.32		$1,116.5882	$1,116.61	$1,116.65	$1,116.40