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	$104.96	8.675%	$114.0653	$114.07	$114.05	$114.10
Purchase #2	$187.99	3.422%	$194.423	$194.42	$194.40	$194.40
Purchase #3	$136.47	11.779%	$152.5448	$152.54	$152.55	$152.50
Purchase #4	$196.72	11.472%	$219.2877	$219.29	$219.30	$219.30
Purchase #5	$127.56	9.655%	$139.8759	$139.88	$139.90	$139.90
Purchase #6	$245.43	10.873%	$272.1156	$272.12	$272.10	$272.10
Purchase #7	$158.77	12.581%	$178.7449	$178.74	$178.75	$178.70
7 purchase totals =	$1,157.90		$1,271.0572	$1,271.06	$1,271.05	$1,271.00