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	$96.29	7.782%	$103.7833	$103.78	$103.80	$103.80
Purchase #2	$224.28	13.834%	$255.3069	$255.31	$255.30	$255.30
Purchase #3	$153.69	6.873%	$164.2531	$164.25	$164.25	$164.30
Purchase #4	$107.92	9.734%	$118.4249	$118.42	$118.40	$118.40
Purchase #5	$161.66	4.707%	$169.2693	$169.27	$169.25	$169.30
Purchase #6	$115.35	6.818%	$123.2146	$123.21	$123.20	$123.20
Purchase #7	$206.37	8.486%	$223.8826	$223.88	$223.90	$223.90
7 purchase totals =	$1,065.56		$1,158.1347	$1,158.12	$1,158.10	$1,158.20