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	$219.56	5.630%	$231.9212	$231.92	$231.90	$231.90
Purchase #2	$163.67	7.108%	$175.3037	$175.30	$175.30	$175.30
Purchase #3	$165.33	10.806%	$183.1956	$183.20	$183.20	$183.20
Purchase #4	$116.28	3.448%	$120.2893	$120.29	$120.30	$120.30
Purchase #5	$79.78	7.195%	$85.5202	$85.52	$85.50	$85.50
Purchase #6	$115.55	6.789%	$123.3947	$123.39	$123.40	$123.40
Purchase #7	$174.36	8.729%	$189.5799	$189.58	$189.60	$189.60
7 purchase totals =	$1,034.53		$1,109.2046	$1,109.20	$1,109.20	$1,109.20