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	$145.56	10.784%	$161.2572	$161.26	$161.25	$161.30
Purchase #2	$238.32	7.575%	$256.3727	$256.37	$256.35	$256.40
Purchase #3	$94.55	6.668%	$100.8546	$100.85	$100.85	$100.90
Purchase #4	$187.69	6.494%	$199.8786	$199.88	$199.90	$199.90
Purchase #5	$142.43	9.219%	$155.5606	$155.56	$155.55	$155.60
Purchase #6	$183.37	6.494%	$195.278	$195.28	$195.30	$195.30
Purchase #7	$85.46	7.547%	$91.9097	$91.91	$91.90	$91.90
7 purchase totals =	$1,077.38		$1,161.1114	$1,161.11	$1,161.10	$1,161.30