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	$90.56	11.348%	$100.8367	$100.84	$100.85	$100.80
Purchase #2	$136.30	9.661%	$149.4679	$149.47	$149.45	$149.50
Purchase #3	$86.54	6.696%	$92.3347	$92.33	$92.35	$92.30
Purchase #4	$192.60	6.730%	$205.562	$205.56	$205.55	$205.60
Purchase #5	$197.89	7.585%	$212.9	$212.90	$212.90	$212.90
Purchase #6	$135.50	6.366%	$144.1259	$144.13	$144.15	$144.10
Purchase #7	$103.44	5.538%	$109.1685	$109.17	$109.15	$109.20
7 purchase totals =	$942.83		$1,014.3957	$1,014.40	$1,014.40	$1,014.40