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	$55.36	13.336%	$62.7428	$62.74	$62.75	$62.70
Purchase #2	$114.32	11.410%	$127.3639	$127.36	$127.35	$127.40
Purchase #3	$227.91	9.271%	$249.0395	$249.04	$249.05	$249.00
Purchase #4	$208.28	4.874%	$218.4316	$218.43	$218.45	$218.40
Purchase #5	$122.55	7.470%	$131.7045	$131.70	$131.70	$131.70
Purchase #6	$57.83	6.209%	$61.4207	$61.42	$61.40	$61.40
Purchase #7	$170.88	10.368%	$188.5968	$188.60	$188.60	$188.60
7 purchase totals =	$957.13		$1,039.2998	$1,039.29	$1,039.30	$1,039.20