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	$18.31	4.823%	$19.1931	$19.19	$19.20	$19.20
Purchase #2	$76.69	5.484%	$80.8957	$80.90	$80.90	$80.90
Purchase #3	$85.49	12.556%	$96.2241	$96.22	$96.20	$96.20
Purchase #4	$155.83	6.778%	$166.3922	$166.39	$166.40	$166.40
Purchase #5	$104.27	9.553%	$114.2309	$114.23	$114.25	$114.20
Purchase #6	$98.40	13.145%	$111.3347	$111.33	$111.35	$111.30
Purchase #7	$197.36	6.779%	$210.739	$210.74	$210.75	$210.70
7 purchase totals =	$736.35		$799.0097	$799.00	$799.05	$798.90