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	$166.28	3.474%	$172.0566	$172.06	$172.05	$172.10
Purchase #2	$134.93	9.593%	$147.8738	$147.87	$147.85	$147.90
Purchase #3	$232.95	7.805%	$251.1317	$251.13	$251.15	$251.10
Purchase #4	$57.75	8.568%	$62.698	$62.70	$62.70	$62.70
Purchase #5	$72.93	7.681%	$78.5318	$78.53	$78.55	$78.50
Purchase #6	$62.45	6.653%	$66.6048	$66.60	$66.60	$66.60
Purchase #7	$134.36	12.780%	$151.5312	$151.53	$151.55	$151.50
7 purchase totals =	$861.65		$930.4279	$930.42	$930.45	$930.40