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	$240.32	12.190%	$269.615	$269.62	$269.60	$269.60
Purchase #2	$185.32	6.250%	$196.9025	$196.90	$196.90	$196.90
Purchase #3	$13.58	4.689%	$14.2168	$14.22	$14.20	$14.20
Purchase #4	$97.54	13.166%	$110.3821	$110.38	$110.40	$110.40
Purchase #5	$114.51	10.339%	$126.3492	$126.35	$126.35	$126.30
Purchase #6	$168.72	5.855%	$178.5986	$178.60	$178.60	$178.60
Purchase #7	$111.73	5.799%	$118.2092	$118.21	$118.20	$118.20
7 purchase totals =	$931.72		$1,014.2734	$1,014.28	$1,014.25	$1,014.20