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	$195.84	6.412%	$208.3973	$208.40	$208.40	$208.40
Purchase #2	$240.41	5.330%	$253.2239	$253.22	$253.20	$253.20
Purchase #3	$59.91	12.846%	$67.606	$67.61	$67.60	$67.60
Purchase #4	$53.40	6.352%	$56.792	$56.79	$56.80	$56.80
Purchase #5	$5.86	6.296%	$6.2289	$6.23	$6.25	$6.20
Purchase #6	$12.61	13.810%	$14.3514	$14.35	$14.35	$14.40
Purchase #7	$59.64	11.295%	$66.3763	$66.38	$66.40	$66.40
7 purchase totals =	$627.67		$672.9758	$672.98	$673.00	$673.00