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	$95.26	11.488%	$106.2035	$106.20	$106.20	$106.20
Purchase #2	$178.69	6.129%	$189.6419	$189.64	$189.65	$189.60
Purchase #3	$125.43	7.600%	$134.9627	$134.96	$134.95	$135.00
Purchase #4	$173.91	3.108%	$179.3151	$179.32	$179.30	$179.30
Purchase #5	$108.31	5.590%	$114.3645	$114.36	$114.35	$114.40
Purchase #6	$127.79	9.242%	$139.6004	$139.60	$139.60	$139.60
Purchase #7	$178.48	10.156%	$196.6064	$196.61	$196.60	$196.60
7 purchase totals =	$987.87		$1,060.6945	$1,060.69	$1,060.65	$1,060.70