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	$43.87	12.711%	$49.4463	$49.45	$49.45	$49.40
Purchase #2	$231.31	7.831%	$249.4239	$249.42	$249.40	$249.40
Purchase #3	$46.29	9.714%	$50.7866	$50.79	$50.80	$50.80
Purchase #4	$146.27	11.194%	$162.6435	$162.64	$162.65	$162.60
Purchase #5	$209.82	6.692%	$223.8612	$223.86	$223.85	$223.90
Purchase #6	$119.33	3.671%	$123.7106	$123.71	$123.70	$123.70
Purchase #7	$176.78	10.815%	$195.8988	$195.90	$195.90	$195.90
7 purchase totals =	$973.67		$1,055.7709	$1,055.77	$1,055.75	$1,055.70