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	$82.55	4.662%	$86.3985	$86.40	$86.40	$86.40
Purchase #2	$172.45	4.554%	$180.3034	$180.30	$180.30	$180.30
Purchase #3	$94.66	8.117%	$102.3436	$102.34	$102.35	$102.30
Purchase #4	$96.31	4.204%	$100.3589	$100.36	$100.35	$100.40
Purchase #5	$233.96	10.326%	$258.1187	$258.12	$258.10	$258.10
Purchase #6	$175.79	7.672%	$189.2766	$189.28	$189.30	$189.30
Purchase #7	$169.91	8.275%	$183.9701	$183.97	$183.95	$184.00
7 purchase totals =	$1,025.63		$1,100.7698	$1,100.77	$1,100.75	$1,100.80