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	$171.94	7.102%	$184.1512	$184.15	$184.15	$184.20
Purchase #2	$101.75	7.166%	$109.0414	$109.04	$109.05	$109.00
Purchase #3	$142.74	6.280%	$151.7041	$151.70	$151.70	$151.70
Purchase #4	$126.80	8.357%	$137.3967	$137.40	$137.40	$137.40
Purchase #5	$136.25	4.527%	$142.418	$142.42	$142.40	$142.40
Purchase #6	$69.39	7.128%	$74.3361	$74.34	$74.35	$74.30
Purchase #7	$64.73	11.669%	$72.2833	$72.28	$72.30	$72.30
7 purchase totals =	$813.60		$871.3308	$871.33	$871.35	$871.30