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	$181.42	8.164%	$196.2311	$196.23	$196.25	$196.20
Purchase #2	$131.32	9.343%	$143.5892	$143.59	$143.60	$143.60
Purchase #3	$27.47	6.730%	$29.3187	$29.32	$29.30	$29.30
Purchase #4	$120.42	7.410%	$129.3431	$129.34	$129.35	$129.30
Purchase #5	$143.40	6.460%	$152.6636	$152.66	$152.65	$152.70
Purchase #6	$46.86	11.566%	$52.2798	$52.28	$52.30	$52.30
Purchase #7	$148.44	9.384%	$162.3696	$162.37	$162.35	$162.40
7 purchase totals =	$799.33		$865.7951	$865.79	$865.80	$865.80