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	$180.73	5.286%	$190.2834	$190.28	$190.30	$190.30
Purchase #2	$124.40	10.375%	$137.3065	$137.31	$137.30	$137.30
Purchase #3	$137.55	5.553%	$145.1882	$145.19	$145.20	$145.20
Purchase #4	$165.53	3.568%	$171.4361	$171.44	$171.45	$171.40
Purchase #5	$12.74	9.402%	$13.9378	$13.94	$13.95	$13.90
Purchase #6	$245.57	5.872%	$259.9899	$259.99	$260.00	$260.00
Purchase #7	$91.88	9.520%	$100.627	$100.63	$100.65	$100.60
7 purchase totals =	$958.40		$1,018.7689	$1,018.78	$1,018.85	$1,018.70