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	$85.46	4.292%	$89.1279	$89.13	$89.15	$89.10
Purchase #2	$200.90	5.452%	$211.8531	$211.85	$211.85	$211.90
Purchase #3	$94.68	10.256%	$104.3904	$104.39	$104.40	$104.40
Purchase #4	$194.33	8.783%	$211.398	$211.40	$211.40	$211.40
Purchase #5	$185.37	7.145%	$198.6147	$198.61	$198.60	$198.60
Purchase #6	$89.91	13.574%	$102.1144	$102.11	$102.10	$102.10
Purchase #7	$125.73	8.202%	$136.0424	$136.04	$136.05	$136.00
7 purchase totals =	$976.38		$1,053.5409	$1,053.53	$1,053.55	$1,053.50