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	$96.86	4.616%	$101.3311	$101.33	$101.35	$101.30
Purchase #2	$136.70	11.158%	$151.953	$151.95	$151.95	$152.00
Purchase #3	$40.84	5.590%	$43.123	$43.12	$43.10	$43.10
Purchase #4	$39.56	10.815%	$43.8384	$43.84	$43.85	$43.80
Purchase #5	$169.82	9.857%	$186.5592	$186.56	$186.55	$186.60
Purchase #6	$67.71	9.256%	$73.9772	$73.98	$74.00	$74.00
Purchase #7	$227.76	5.569%	$240.444	$240.44	$240.45	$240.40
7 purchase totals =	$779.25		$841.2259	$841.22	$841.25	$841.20