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	$71.71	4.314%	$74.8036	$74.80	$74.80	$74.80
Purchase #2	$135.52	4.250%	$141.2796	$141.28	$141.30	$141.30
Purchase #3	$236.88	10.339%	$261.371	$261.37	$261.35	$261.40
Purchase #4	$18.88	7.572%	$20.3096	$20.31	$20.30	$20.30
Purchase #5	$146.50	3.507%	$151.6378	$151.64	$151.65	$151.60
Purchase #6	$126.82	12.366%	$142.5026	$142.50	$142.50	$142.50
Purchase #7	$196.80	12.198%	$220.8057	$220.81	$220.80	$220.80
7 purchase totals =	$933.11		$1,012.7099	$1,012.71	$1,012.70	$1,012.70