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	$87.55	3.843%	$90.9145	$90.91	$90.90	$90.90
Purchase #2	$131.28	6.196%	$139.4141	$139.41	$139.40	$139.40
Purchase #3	$114.35	5.520%	$120.6621	$120.66	$120.65	$120.70
Purchase #4	$158.82	4.120%	$165.3634	$165.36	$165.35	$165.40
Purchase #5	$211.26	7.731%	$227.5925	$227.59	$227.60	$227.60
Purchase #6	$158.71	3.832%	$164.7918	$164.79	$164.80	$164.80
Purchase #7	$135.94	12.752%	$153.2751	$153.28	$153.30	$153.30
7 purchase totals =	$997.91		$1,062.0135	$1,062.00	$1,062.00	$1,062.10