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	$110.80	11.843%	$123.922	$123.92	$123.90	$123.90
Purchase #2	$91.62	9.583%	$100.3999	$100.40	$100.40	$100.40
Purchase #3	$150.59	5.274%	$158.5321	$158.53	$158.55	$158.50
Purchase #4	$84.76	11.763%	$94.7303	$94.73	$94.75	$94.70
Purchase #5	$195.95	9.630%	$214.82	$214.82	$214.80	$214.80
Purchase #6	$101.46	9.315%	$110.911	$110.91	$110.90	$110.90
Purchase #7	$217.33	13.520%	$246.713	$246.71	$246.70	$246.70
7 purchase totals =	$952.51		$1,050.0283	$1,050.02	$1,050.00	$1,049.90