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	$142.51	6.872%	$152.3033	$152.30	$152.30	$152.30
Purchase #2	$209.37	8.687%	$227.558	$227.56	$227.55	$227.60
Purchase #3	$68.55	12.151%	$76.8795	$76.88	$76.90	$76.90
Purchase #4	$149.40	11.285%	$166.2598	$166.26	$166.25	$166.30
Purchase #5	$203.61	4.402%	$212.5729	$212.57	$212.55	$212.60
Purchase #6	$125.45	4.677%	$131.3173	$131.32	$131.30	$131.30
Purchase #7	$84.65	5.859%	$89.6096	$89.61	$89.60	$89.60
7 purchase totals =	$983.54		$1,056.5004	$1,056.50	$1,056.45	$1,056.60