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	$62.76	12.399%	$70.5416	$70.54	$70.55	$70.50
Purchase #2	$91.37	7.847%	$98.5398	$98.54	$98.55	$98.50
Purchase #3	$225.96	8.627%	$245.4536	$245.45	$245.45	$245.50
Purchase #4	$73.94	9.696%	$81.1092	$81.11	$81.10	$81.10
Purchase #5	$186.35	12.286%	$209.245	$209.25	$209.25	$209.20
Purchase #6	$176.33	13.664%	$200.4237	$200.42	$200.40	$200.40
Purchase #7	$145.57	12.674%	$164.0195	$164.02	$164.00	$164.00
7 purchase totals =	$962.28		$1,069.3324	$1,069.33	$1,069.30	$1,069.20