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	$121.44	5.378%	$127.971	$127.97	$127.95	$128.00
Purchase #2	$185.71	7.440%	$199.5268	$199.53	$199.55	$199.50
Purchase #3	$170.61	6.813%	$182.2337	$182.23	$182.25	$182.20
Purchase #4	$29.33	3.348%	$30.312	$30.31	$30.30	$30.30
Purchase #5	$218.66	10.161%	$240.878	$240.88	$240.90	$240.90
Purchase #6	$151.82	9.728%	$166.589	$166.59	$166.60	$166.60
Purchase #7	$64.87	11.660%	$72.4338	$72.43	$72.45	$72.40
7 purchase totals =	$942.44		$1,019.9443	$1,019.94	$1,020.00	$1,019.90