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	$27.95	3.153%	$28.8313	$28.83	$28.85	$28.80
Purchase #2	$205.88	10.369%	$227.2277	$227.23	$227.25	$227.20
Purchase #3	$144.55	8.216%	$156.4262	$156.43	$156.45	$156.40
Purchase #4	$146.40	3.197%	$151.0804	$151.08	$151.10	$151.10
Purchase #5	$237.60	6.199%	$252.3288	$252.33	$252.35	$252.30
Purchase #6	$162.92	7.719%	$175.4958	$175.50	$175.50	$175.50
Purchase #7	$105.88	3.314%	$109.3889	$109.39	$109.40	$109.40
7 purchase totals =	$1,031.18		$1,100.7791	$1,100.79	$1,100.90	$1,100.70