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	$185.28	10.363%	$204.4806	$204.48	$204.50	$204.50
Purchase #2	$51.85	8.316%	$56.1618	$56.16	$56.15	$56.20
Purchase #3	$206.53	8.752%	$224.6055	$224.61	$224.60	$224.60
Purchase #4	$240.27	4.313%	$250.6328	$250.63	$250.65	$250.60
Purchase #5	$176.96	5.501%	$186.6946	$186.69	$186.70	$186.70
Purchase #6	$31.89	5.868%	$33.7613	$33.76	$33.75	$33.80
Purchase #7	$41.90	7.538%	$45.0584	$45.06	$45.05	$45.10
7 purchase totals =	$934.68		$1,001.3950	$1,001.39	$1,001.40	$1,001.50